This paper is a summary of my nanolithography research on thin films of lanthanum barium manganese oxide (LBMO). I used an atomic force microscope to create line patterns on LBMO thin films that were grown under different oxygen pressures. My goal was to determine a relationship between the height of the line pattern on the film and the oxygen pressure that was used to create it.

1. AFM Nanolithography of Lanthanum Barium Manganese Oxide (LaBaMnO3)Thin Films: The
Effect of Oxygen Pressure Variations During Film Growth
Christopher Stumpf
Towson University
Abstract
In AFMnanolithography,abiasvoltage appliedbetweenthe tipof an atomicforce microscope
(AFM) and a sample isusedtoproduce nanoscale modificationsof material surfaces.AFM
nanolithographyhasbeenstudiedextensivelyonavarietyof materials,butlimitedstudieshave been
performedonperovskite manganitessuchas LanthanumBariumManganese Oxide (LBMO).Studying
such materialsisimportantbecause of theirpotentialapplicationsforroom-temperature nanoscale
spintronicdevices.PreviousresearchonLBMO by our grouphas focusedonhow parameterssuchas
appliedtipvoltage,temperature,andhumidityaffectthe creationof nanopatterns.Thispaperreports
on the influenceof growthpressure of the LBMO filmsgrownbypulsedlaserdeposition.Filmsgrownon
(100) SrTiO3 were studiedforgrowthpressuresrangingbetween100mTorr to 400 mTorr. Our studies
indicate thatthe type of nanopatternsinducedbyAFMand the relaxationdynamicsof these patterns
are sensitivetothe filmgrowthpressure. The growthpressureismainlyknowntoaffectthe oxygen
concentrationandthe surface roughness,butpossiblevariationsincationicstoichiometrycouldalso
contribute tothese results.

2. Introduction
AFMnanolithographyonperovskitemanganitesisanew researchfieldwithimportant
applications. Perovskite manganitessuch aslanthanumbariummanganese oxide (LBMO) could
potentiallybe usedtocreate room-temperature nanoscale spintronicdevices. Since the fieldissonew,
there isverylittle publishedresearchonLBMO.The few papersthathave beenpublishedbyTowson
UniversityandDr.Run-Wei Li have focusedonhow parameterssuchas humidityandtipvoltage affect
the growthof nanopatternsonthe thinfilm[1].
My researchfocusesonhowthe growthpressure of LBMO filmsgrownbypulsedlaser
depositionaffectsthe nanopatterns. The growthpressure influencesthe oxygenconcentrationand
surface roughnessof the LBMO film. IworkedwithLMBO filmsgrownat 50 mTorr, 100 mTorr, 225
mTorr, and 400 mTorr. I performednanolithographyoneachfilmandcomparedthe resultsto
determine howgrowthpressureaffectsthe creationof nanopatterns.
Theory
The science behindAFMnanolithographyonperovskite manganitesisnotcompletely
understood. Formetalsandsemiconductors,anodicoxidation isthe processusedtocreate nanoscale
patterns.Inanodicoxidationthe sample isplacedinahumidenvironmenttoallow awatermeniscusto
formon the sample’ssurface.A voltage biasisthenappliedbetweenthe tipandthe sample which
generatesanintense electricfieldaroundthe tip[1].The electricfieldionizeswatermoleculesinthe
meniscustocreate negativelychargedoxygenionswhich reactwiththe metal sample toforman oxide
filmonthe sample’ssurface [1].
Anodicoxidationisnotthe only processbehindAFMnanolithographyonperovskite oxides.
Accordingto Dr. Run-Wei Li,the reasonisthat AFMnanolithographycanbe performedonsamplesthat
do nothave many oxygenvacancies[1]. Dr.Li discoveredthat“oxygenvacanciesare notindispensable
for AFMlithographyinperovskiteoxides.Asaresult,anodicoxidationshouldnotbe the mainphysical
processof AFMlithographyin perovskiteoxides.[1]”There maybe some anodicoxidationduringAFM
nanolithography butitlikelyonlyoccursatthe sample’ssurface [1]. Instead, Dr.Li theorizesthat
chemical transportprocessessuchaselectromigrationandfield-induceddiffusion mightoccurduring
nanolithographydue tothe intenseelectricfieldbetweenthe AFMtip andsample surface [1]. Overall
there are likelyseveral processesatwork duringAFMnanolithographyonperovskite oxides.
Experimental Procedure
Sample Creation
For my researchIcreatedfour LBMO filmsunderdifferentgrowthpressures.Each filmwas
grownon a SrTiO3 (100) substrate bypulsedlaserdepositionusingakryptonfluoride laser. The laser
operatedata wavelengthof 248 nmand a frequencyof 10 Hz. The substrate wasplacedinside a
depositionchamberwhichcontained anO2 atmosphere underagrowthpressure.Ichanged the growth
pressure foreachsample. Duringdeposition the substrate washeatedto800°C and thenhitby 10,000

3. laserpulses withanenergyof 450 mJ. Afterdepositionthe newlygrownLBMOfilmwascooleddownto
room temperature inanoxygenenvironmentat 500 mTorr witha coolingrate of 20°C perminute.The
onlyparameterthatI changedbetweenthe fourfilmdepositionswasthe growthpressure.Icreated
filmswithgrowthpressuresof 50mTorr, 100 mTorr, 225 mTorr, and 400 mTorr.The growthpressure
affectsthe oxygenconcentrationandsurface roughnessof eachfilm. A higherpressure resultsina
higheroxygenconcentrationandarougherfilmsurface.
Scanning and Writing on the LBMO Films
I performedmynanolithographyexperimentsusingaVeeco Multimode V scanningprobe
microscope operatingincontactmode withsilicontipsmade byAsylumResearch. Iusedthe custom
made LabViewprogram “LC parallel Ylinesvoltage increments.vi” towrite line patterns onthe samples.
The program worksby movingthe AFMtipacross the sample’ssurface while applyingavoltage biasto
the tip.At highhumidity,the tipvoltage causesanoxide toform onthe sample.Afteritfinisheswriting
one line the programincrementsthe voltage andmovestoanew locationto write the nextline.
I usedthe LabViewprogram tocreate a patternof 11 linesina20 µm scan area. The linesI
createdare 16 µm longand are spaced 2 µm apart. I wrote the linesinvoltage rangessuchas 10V to
20V, 20V to 30V, and -15V to -5V among others. Iwrote 11 linessothat I couldcompare the linesatthe
endof the voltage ranges.Forexample,Icomparedthe heightof a20V line writtenlast inthe 10V to
20V range withthe heightof a 20V line writtenfirstinthe 20V to 30V range.I wantedto see if the order
of writingaffectedthe line’sheight.
All of my line patternswere createdata temperature of roughly70 °F anda humiditylevel
between60%and75%. I usedan AFM writingspeedof 1.6 µm/s. I createdmultiplelinepatternsfor
each voltage range.Ithenused Nanoscope tomeasure the heightandwidthof eachline inthe pattern. I
averagedtogetherthe resultsfromeachpatterntodetermine the average heightandwidth of the line
that eachappliedvoltage produced. Ialsomeasuredthe standarddeviationof the line heights.Mygoal
was to determinehowwellthe nanolithographyprocesscouldbe controlled.Ialsowantedtosee if the
line patternscouldbe easilyreproduced. Ihave includedanexampledatatable onthe lastpage.
Growth Pressure and Surface Roughness
The growth pressure hasa majorimpact onthe sample’ssurface roughness.Samplesthatare
grownat highgrowthpressures suchas400 mTorr are rougherthansamplesgrownat low pressures
like 50 mTorr. Sample LBMO-STO-34was createdat the lowestgrowthpressure of 50 mTorr while
sample LBMO-STO-37was grownat the highestpressure of 400 mTorr. Sample LBMO-STO-39was
createdat 225 mTorr and sample LBMO-STO- 43 was grown at 100 mTorr. (Iwill refertoeach sample by
itsnumber. I will alsolistthe growthpressure inparenthesesafterthe sample name forclarity.)
Figure 1 consistsof four AFMheightimagesthatshow the surface roughnessof eachsample.
Each example image isagoodrepresentationof the roughnessof the whole sample. Figure1showsthat
a highgrowth pressure will resultinaroughersample surface. The differencesinsurface roughnesscan
alsobe seennumerically. IusedNanoscope’sroughnesscommandtocalculate the average roughness

4. (Ra) of each sample.The average roughnessof sample34 (50 mTorr) was0.442 nm while the average
roughnessof sample 43 (100 mTorr) was 0.973 nm.For the highergrowthpressures,the average
roughnesswas2.056 nm for sample 39 (225 mTorr) and 1.356 nm for sample 37 (400 mTorr). High grow
pressurescause large dotsto appearonthe sample’ssurface.Mostof the dotsare lessthan10 nm in
heightbuta fewdotscan be 40 nm or more. The dots can make writingdifficultbutnanolithographyis
still possible onhighgrowthpressure samples.
Figure 1: Example imagesshowingthe surface roughnessforeachgrowthpressure
(a) 50 mTorr surface(sample34) (b) 100 mTorr surface(sample43)
(c) 225 mTorr surface(sample39) (d) 400 mTorr surface(sample37)
Results
50 mTorr sample, LBMO-STO-34
Sample LBMO-STO-34was createdon May 3, 2013 witha growthpressure of 50 mTorr. The sample has
a verysmoothsurface whichmade it easyto write upon. There are few defectsonthe sample’ssurface.
Positive Applied Tip Voltages on Sample 34 (50 mTorr)
I appliedpositive tipvoltagesbetween1V and30V to sample 34 (50 mTorr) inorder to create
line patterns.Iusedthe LabViewprogramtowrite either11 linesina20 µm area or 21 linesina32 µm
area. I createdline patterns inthe followingvoltage ranges:1V to 10V, 1V to 20V, 5V to 15V, 5V to 25V,
10V to20V, 15V to 25V, 20V to 30V, and 10V to 30V. Figure 2 showsthree examplesof positive voltage

5. line patternsonsample 34 (50 mTorr). The lowestvoltage line isthe leftmostline inthe images.Each
subsequentline waswrittenat1V largerthan the previousline.
Figure 2: Example imagesof positive voltage linepatternsonsample 34
(a) 10V to 20V linepattern (b) 10V to 30V linepattern (c) 10V to 30V linepattern
The qualityof the linesproducedbypositivetipvoltagescanvarygreatly dependingonthe
humidity.Figure 2(a) and(b) showclean,well definedlineswhile image (c) showsablurry,jaggedline
pattern. Images(a) and(b) were createdat 73% humiditywhile image(c) wascreatedat 80% humidity.
A small increase inthe humiditycancause the linestogrow uncontrollably.
I performeddozensof positivetipvoltage testsonsample 34(50 mTorr).Afterwriting,I used
the stepfunctioninNanoscope tomeasure the heightandwidthof eachline.Iaveragedthe results
togethertodetermine the average heightof the line eachvoltage produces.I didthisinorderto see
howcontrollable the writingprocessisandif the resultsare reproducible.Figure 3onthe nextpage isa
graph of positive tipvoltagesversusthe average lineheightof voltage.The vertical errorbarsare the
standarddeviationsof the line heights. Icalculatedthe standarddeviationswith the STDEV functionin
MicrosoftExcel.
As seeninFigure 3,the average line heightincreaseslinearlywiththe voltage.The smallestline
heightwas0.184 nmat 5V while the largestheightwas27.1 nm at 30V. Highvoltageswill produce
largerlinesthansmall voltages. Howeveragivenvoltage canproduce lineswithwidelyvaryingheights.
For example,inmytestsa15V appliedtipvoltage producedlineswithheightsof 3.73 nm, 7.36 nm, and
13.2 nm among others. AsseeninFigure 3,the standard deviation isverylarge formostof the positive
appliedtipvoltages. The 5V line hasthe loweststandarddeviationof 0.3825 nm while the 19V line has
the highestdeviationof 4.361 nm. The standarddeviationsforsample34 (50 mTorr) are higherthanthe
standarddeviationsof the otherLBMO samplesthatI will discusslater.
Figure 3 showsthat linesdonotappearunlessa voltage of at least5V is appliedtothe AFMtip.
Appliedvoltagessmallerthan5V donot create any growthson the sample.The minimumvoltage at
whichlinesare formedonthe sample iscalledthe threshold voltage.5V isthe thresholdvoltage for
sample 34 (50 mTorr).In hiswork onLBMO, Dr. Run-Wei Li foundthatthere wasalso a voltage atwhich
the lineswouldnotgetlargerevenif highervoltageswere appliedtothe tip.He calledthisthe
10 V 10 V 10 V30 V 30 V20 V

6. saturationpoint.My data shows thatthe 50 mTorr sample 34 doesnot have a saturationpointbecause
the line heightskeepincreasingasthe voltage increases.OthersamplesthatIwill discusslaterdohave
saturationpoints.
Figure 3: Positive tipvoltagevs.average lineheightwithstandarddeviationbars
In additiontothe heights,Ialsomeasuredeachline’swidth.Figure4showsthe average line width
producedbyeach voltage. Unlike the heights, the line widthshave asaturationpoint.
Figure 4: Positive tipvoltagesvs.average linewidth withstandarddeviationbars
The average line widthsrangedfrom0.755 µm to 0.976 µm. The smallestlinewidthwas0.461 µm while
the largestwidthwas1.213 µm. Applyingverylarge voltagesonlymade the linestaller, notwider.
I createdline patternswith11 or 21 linesbecause Iwantedtosee if the orderinwhichthe lines
are written affectstheirheight. A line couldbe writtenfirst,last,orinthe middle of avoltage range. On
sample 34 (50 mTorr),the writingordercaninfluence the line’sheight. Mydata for the 20V line isa
0
5
10
15
20
0 5 10 15 20 25 30
AverageLineHeight(nm)
Voltage (V)
LBMO-STO-34 (50 mTorr) Positive Tip Voltage vs.
Average Line Height
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5 10 15 20 25 30
AverageLineWidth(µm)
Voltage (V)
LBMO-STO-34 (50 mTorr) Positive Tip Voltage vs.
Average Line Width

7. goodexample of the behavior.The 20V line waswrittenlastinthe 10V to 20V line patterns andfirstin
the 20V to 30V patterns.It waswritteninthe middle of the patterninthe 10V to 30V range. Table 1
belowshowsthe heightof 20V lineswrittenatdifferentpointsinthe writingprocess.
Table 1: 20V line dataon sample 34
OrderWritten Line Heights (nm) Average line height inbold(nm)
20V line writtenfirst (20V to 30V) 4.61 2.48 3.73 6.62 1.97 8.34 4.11 4.55
20V line writtenin the middle (10V to30V) 5.18 10.4 6.46 6.68 8.66 5.43 5.65 6.92
20V line writtenlast (10V to20V) 13.7 14.4 10.6 17.3 9.42 10.1 12.6 12.6
As Table 1 shows,the writingorderaffectsthe heightof the createdline onsample 34(50 mTorr).The
20V line isnotunique;other positive tipvoltagesproducedsimilarresultsonsample 34. However,this
behaviordidnot occur on samples37, 39, and 43 whichall have highergrowthpressures.Itmaybe
unique tothe 50 mTorr growth pressure.
Negative Applied Tip Voltages on Sample 34 (50 mTorr)
Negative appliedtipvoltages produce uncontrollable growths onsample 34. Negative tip
voltagesusuallyproduce massivegrowths,huge partial line patterns,ortrenchesinthe film.Figure 5
showsexample imagesof these three results.
Figure 5: Example imagesof negative tipvoltagesonsample 34
(a) Massivegrowth (b) Huge linepattern (c) Trenches in the film
Massive growthslike Figure 5(a) are the most commonresultof applyinganegative tipvoltage
to sample 34 (50 mTorr). The growthinimage (a) was producedbyapplyinga -15V tipvoltage to sample
34 witha humiditylevel of 70%. It coversan area of roughly1600 µm2
and hasa maximumheightof
over1 µm. The growthis so large itcan actuallybe seenonthe TV monitorthatishookedupto the
AFM. Massive growthslike image (a) usuallyformwhenthe humiditylevelisabove 60% and the applied
voltage is -5V or greater.
If the humiditylevelis 45% or lowerhuge line patternswill sometimes forminsteadof massive
growths. Figure 5 (b) isan example of ahuge line pattern.The patterninimage (b) wascreatedby
applyingnegativetipvoltagesrangingfrom -15V to -5V to sample 34 at a humidityof 45%. The tip
-15 V

8. writingspeedwas1.6 µm/s.The linesinimage (b) are verylarge comparedto the positive voltagelines.
The -15V line inimage (b) is123 nmtall while the otherlinesrange from98 nm to 30 nm inheight.The
huge linesdonotalwaysappearwhenthe humidityislower.Sometimesmassivegrowthsoccureven
whenthe humidityislessthan45%. Negative voltagesproduce uncontrollableresults.
In rare occasions,trencheswillsometimesformonthe LBMO filminsteadof massive growthsor
huge lines.Figure 5(c) is an example of atrenchinthe film.Image (c) wascreatedby applyingvoltages
rangingfrom-20V to -10V to sample 34 at a humiditylevel of 70%.The createdtrenchesare roughly10
nm deep. Trenchesare muchrarer thangrowthsor huge line patterns.Ihave onlyhadtwotrenches
formon sample 34 while conductingdozensof negative voltage tests
Finally,applyingasmall negativevoltage tosample 34at a low humiditywill produce no
reactionat all. I applieda-5V tipvoltage to sample 34 at a humidityof 40%.No reactionoccurredduring
thistest. Nogrowthsformedand the sample wasunchanged. There isathresholdvoltage of
approximately -5V fornegative voltagesonsample 34.Voltageslowerthan -5V do notproduce growths
evenif the humidityisveryhigh.
Pattern Relaxation and Surface Aging on Sample 34 (50 mTorr)
In hisworkon LBMO, Dr. Run-Wei Li discoveredthatthe line patternswouldshrinkand
disappearaftera certainperiodof time.He calledthisphenomenonrelaxation.Iperformedtestsonall
fourof my LBMO samplestosee if they alsoexperiencedrelaxation. Inmytests,Iwrote a line pattern
on a Fridayafternoon andthenleftthe sample inthe AFMfor approximately72 hoursbefore rescanning
the pattern. I alsoperformedteststosee how the surface of the sample changedwithage.The LBMO
samplestendto become rougherastheyage.
I discoveredthatsample 34doesnot experience anyrelaxation.Insteadthe linepatterns
seemedtoslightlygrowoverthe 72 hourperiod.Ialso discoveredthataginghasmade sample 34 more
difficulttowrite on.Itriedto write a10V to 20V line patternonsample 34 inMay 2014, one year after
the sample wascreated.The patternedthatI createdwasmuch fainterthanpatternsI createdinMay
2013. I usedthe sample parametersandtipsatboth times.
Sample 34 (50 mTorr) Conclusions
Positive voltagesproduce clearand well definedlinesonsample 34. We coulduse the positive
tipvoltages tocreate advancednanolithographypatterns on50 mTorr LBMO samples.Negativetip
voltagesproduce randomgrowthsandpatterns.The negative voltagesare toouncontrollable touse in
advancednanolithography.
400 mTorr sample, LBMO-STO-37
Sample LBMO-STO-37was createdon September7,2013 witha growth pressure of 400 mTorr.
The highgrowth pressure made sample 37’ssurface muchrougherthan sample 34’s surface. Despite

9. the rough surface,AFMnanolithographycanstill be performedonsample 37.In fact,both positive and
negative tipvoltagesproduce line patternsonsample 37.
Positive Applied Tip Voltages on Sample 37 (400 mTorr)
I createdline patternsonsample 37 by applyingpositivetipvoltagesbetween10V and40V to
the sample.Iwrote 11 lines ineachpattern witha humiditylevel of atleast70% and a tipwritingspeed
of 1.6 µm/s. Figure 6 consistsof three examplesof positive line patternsonsample 37.
Figure 6: Example imagesof positive tipvoltagesonsample 37(400 mTorr)
(a) 10V to 20V linepattern (b) 20V to 30V linepattern (c) 30V to 40V linepattern
Line patternsonsample 37 tendto be rough,blurry, and uneven.The linesare oftenveryfaint
comparedto linesonsample 34 (50 mTorr). Large dotscan form onthe linesasseeninFigure 6images
(b) and (c). In particulardotssometimesformatthe topof the positive voltagelines. Thesedotsmaybe
due to a problemwiththe LabViewprogram.The linesare drawnbythe tip fromthe bottom up.When
the tip reachesthe topit shouldstop applyingavoltage andmove toa new positiontowrite the next
line.Insteaditmaybe applyingthe voltagesfortoolongwhichiscausingthe dotsto form.I made
alterationstothe LabViewprogrambutI wasunable tocompletelyfix thisproblem.
Figure 7 on the nextpage consistsof nine setsof data that have beenaveragedtogethertofind
the average heightof the line eachvoltage produces.Ihave includedthe dataforall nine testsonthe
lastpage. Overall,the line heightsonsample 37are veryclose together.The linesrangedinheightfrom
1.32 nm to 4.81 nm. In contrast,the heightsforsample 34 range from0.184 nmto 27.1 nm.The data for
sample 37 (400 mTorr) has a much lowerstandarddeviationthansample34’sdata.
I was unable tocreate lineswithtipvoltagesbelow 10V.Therefore10V isthe thresholdvoltage
of sample 37 (400 mTorr).Unlike the 50 mTorr sample,sample 37has a saturationheightof
approximately5nm at 40V. The lineswouldnotgoabove 5 nm inheightevenif the appliedtipvoltage
was 40V or larger.Anotherimportantdifference fromsample 34isthat the writingorderdidnotaffect
the line heights.There islittle difference betweenthe heightsof 20V lineswrittenfirstandlast.Finally
the line widthsalsosaturate. The widthsvarydramaticallyinsize. The smallestlinewidthwas0.601 µm
10 V 20 V 20 V 30 V 40 V30 V

10. while the largestwidthwas1.06 µm. Most of the line widthswere inthe 0.6.5µm to 0.95 µm range as
seeninFigure 8. Twolinescreatedbythe same voltage can have verydifferentwidths.Thisledtothe
large standarddeviationsseeninFigure 8.
Figure 7: Positive tipvoltagesvs.average lineheightwithstandarddeviationbars
Figure 8: Positive tipvoltagesvs. average linewidthwithstandarddeviationbars
Negative Applied Tip Voltages on Sample 37 (400 mTorr)
Negative applied tipvoltagesproduce line patternsonsample 37.Negative voltages donot
create massive, uncontrollable growths like on sample 34(50 mTorr).Howeverthe negative voltage
patternsare notcompletelycontrollable. Large dotsusually appearonandbeneaththe linesduringthe
writingprocess. Figure 9consistsof three examplesof negativevoltage patternsonsample 37. Each
example hasdotsonthe firstfewlines. The dotsare usuallylargerandtallerthanthe rest of the line.
Theycan be consideredhighspotsonthe lines.
0
1
2
3
4
5
6
7
5 10 15 20 25 30 35 40
AverageLineHeight(nm)
AppliedTipVoltage (V)
LBMO-STO-37 (400 mTorr) Positive Tip Voltages vs.
Average Line Height
0.50
0.60
0.70
0.80
0.90
1.00
1.10
1.20
5 10 15 20 25 30 35 40
LineWidth(µm)
AppliedTipVoltage (V)
LBMO-STO-37 Positive Tip Voltages vs. Average
Line Width

11. Figure 9: Example imagesof negative tipvoltagesonsample 37(400 mTorr) withdotson the lines
(a) -30V to -20V linepattern (b) -25V to -15V linepattern (c) -25V to -15V linepattern
I wrote negative patternsinthe followingvoltageranges: -30V to-20V, -25V to -15V, and -20V
to -10V. Like the positive voltages,Iwrote 11 linesineachnegative voltage patternwithahumiditylevel
of at least70% and a tip writingspeedof 1.6µm/s. The negative linesare fainterandrougherthanthe
positive voltagelinesonsample 37.The linesoftenhave large dotsonthe firstfew linesalongwithdots
at the bottom.Like the dotson the positive voltage lines,the growthsatthe bottomof the negative
linesare likelycausedbyaproblemwiththe LabViewprogram.The tipislikelyapplyingavoltage at the
bottomfor toolongwhichcauseslarge growths.Unfortunately,Iwasunable tofix thisproblem.
The dots on the actual linesare more random thanthe dotsat the bottom. AsseeninFigure 9,
the dots usuallyonlyformonthe firstthree orfour linesdrawn. The remaininglinesdonothave dots
althoughtheycan be veryfaint.InFigure 9 (a) the dots are onlyon the -30V, -29V and -28V lines. In
image (b) the dotsare on the -25V and -24V linesandin(c) the dots are onthe -25V to -23V lines.The -
25V linesinimages(b) and(c) have dotsonthem.Howeverthe -25V line inimage (a) doesnothave any
dotson it.The -25V line inimage (a) waswritteninthe middle of the writingtestinsteadof atthe
beginninglike in(b) and(c).Thissuggeststhat the writingordercan determinewhere the dotsappear
on the lines. Thisissimilartohowwritingorderaffectedthe line heightsforpositive voltagesonsample
34.
Figure 10 onthe nextpage showsthe average line heightforeachappliednegative voltage on
sample 37 (400 mTorr). The dots onthe linesare includedinthe lineheightmeasurements.The dots
increasedthe heightof the -30V, -29V and-28V lines.Theirincreasedheightcanbe seenonthe leftpart
of the Figure 10 graph. The -27V and -26V linesinimage (a) didnothave any dotson themso their
heightislowerthanthe -30V to -28V lines.AsshowninFigure 9(b) and (c) the -25V to -23V linesalso
had manydots onthem.The dots increasedthe line heightsof those three lineswhichcanbe seenon
the graph. The dots increasedthe line heightbyvariousamountswhichleadtolarge standard
deviationsforthe -25V and-24V lines.The standarddeviationsare 5.50 nmfor the -25V line and5.72
nm forthe -24V line.
-30 V -20 V -15 V-15V -25V-25V
-25 V

12. The -22V to -10V lineshave nodotson themand follow aslightlylinearrelationship.The line
heightsslowlyincreasedasthe voltage became more negative.Fornegativevoltages,sample 37(400
mTorr) hasa thresholdvoltage of -10V.Due tothe presence of the dotson the lines,Icannotdetermine
if sample 37 hasa saturationvoltage andheight.Iwasable tomeasure the line widthswhichare shown
inFigure 11. Evenwiththe dots,mostlineswere roughly0.7µm wide.
Figure 10: Negative tipvoltagesvs.average line heightwithstandarddeviationbars
Figure 11: Negative tipvoltagesvs.average line width withstandarddeviationbars
Pattern Relaxation and Surface Aging on Sample 37 (400 mTorr)
I performedrelaxationtestsonbothpositive andnegativelinepatternsonsample 37.After72
hours,boththe positive andnegative patternshadslightlygrown.The growthforeachline waslessthan
half a nanometer. Sample 37was made inSeptember2013. In May 2014 I attemptedtowrite positive
and negative patternsonthe sample.Iwasable towrite a positive linepatternbutIwascompletely
unable towrite a negative voltage pattern.The positive line patternthatIwasable to write wasfainter
0
5
10
15
20
-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10
AverageLineHeight(nm)
Voltage (V)
LBMO-STO-37 Negative Tip Voltages vs. Average
Line Height
0
0.2
0.4
0.6
0.8
1
-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10
AverageLineWidth(µm)
Voltage (V)
LBMO-STO-37 Negative Voltages vs. Average Line
Width

13. than patternsIwrote back in September2013. Sample 37’sage affectedthe abilitytowrite patternson
it.
Sample 37 (400 mTorr) Conclusions
Althoughthe sample’ssurface isrough,positivetipvoltagesproduce controllableand
reproducible line patternsonsample 37.If the dotsat the top of the linescan be removedsample 37
couldbe usedfor more advancednanolithographyprojects.The linesproducedbynegative tipvoltages
are difficulttocontrol and have many dotson them.Althoughtheydoproduce lines,negative tip
voltagesare toorandom to be usedfornanolithography on400 mTorr samples.
225 mTorr sample, LBMO-STO-39
Sample LBMO-STO-39was createdinNovember, 2013 witha growth pressure of 225 mTorr. I
decidedtouse a 225 mTorr growthpressure because itis exactly inbetweenthe 50mTorr and400
mTorr pressuresof samples34 and37 respectively. Sample39 iscoveredinsmall dotsandgrowths.
There are nocleanareas on the filmsoI had to write the line patternsontopof the dots. I wasable to
write some lineswithbothpositiveandnegative voltages.
Positive Applied Tip Voltages on Sample 39 (225 mTorr)
I wrote positive tipvoltageline patternsonsample 39in the followingvoltage ranges:10V to
20V, 15V to 25V, 20V to 30V, and25V to 35V. Like the previoussamples,Iwrote 11 lineswitha70%
humidity anda 1.6 µm/s writingspeed. Figure12 showsthree positive voltagelinepatternsonsample
39 alongwiththe many dotson the sample.
Figure 12: Example imagesof positive tipvoltagelinepatternsonsample 39(225 mTorr)
(a) 10V to 20V linepattern (b) 20V to 30V linepattern (c) 25V to 35V linepattern
10 V 20 V 30 V20 V 25 V 35 V

14. (d) 25V to 35V linepattern
The drawn linescanvary dramaticallyinheightandwidth. As
seeninFigure 12, two linesrightnexttoeachothercan have
dramaticallydifferentheightsandwidths. The linesinthe middle of
images(b) and(c) are much smallerthanthe linesonthe leftandright
sidesof the images. The difference in size maybe causedbythe many
dotson the sample’ssurface. Since there are somanydots,I had to
write overthemwhencreatingthe line patterns. Inimages(a),(b),and
(c) there are large dotsright nexttothe faintlines. The dotslikely
affectedthe abilityof the tiptodrawncleanlines. Images(c) and(d)
bothshow25V to 35V line patterns.Howeverthe surface of image (d) ismuchcleanerthanimage (c)’s
surface. The tipwas able to create a betterline patternonimage (d) because of itscleanersurface.
The heightsandwidthsof the linescangreatlyvary due to the dotson the sample. Iaveraged
togetherthe varyingheightsandplottedthemversusappliedtipvoltageinFigure 13.
Figure 13: Positive tipvoltagesvs.average line heightwithstandarddeviationbars
The most importantfeature of Figure 13 isthe large standarddeviationbars.The dotsonthe
sample causeda large spreadinmy data whichcan be seeninthe bars. The higheststandarddeviation
was 4.54 nm at the 27V line.The largestvoltage line thatImeasuredwas13.8 nmtall at the 27V line.
The smallestvoltage linewas0.735 nmtall at the 25V line. The 13.8 nm at 27V line appearstobe the
positive voltagesaturationheightandvoltage of sample 39.Like sample 37, sample 39 (225 mTorr) has
a thresholdvoltage of 10V.
The positive voltage lineshave amaximumwidthof 1.171 µm at 30V. The smallestwidthis
0.323 µm at the 11V line.Mostof the line widthsare between 0.4µm and 0.9 µm. The largeststandard
deviationis0.224 µm at 10V.
0
2
4
6
8
10
12
5 10 15 20 25 30 35
AverageLineHeight(nm)
Voltage (V)
LBMO-STO-39 Positive Tip Voltages vs. Average
Line Height
25 V 35 V

15. Figure 14: Positive tipvoltagesvs.average line widthforsample 39 withstandarddeviationbars.
Negative Applied Tip Voltages on Sample 39 (225 mTorr)
For negative linesIused the same writingparametersasthe positivevoltagelines. Iwrote 11
linesineachpatternin voltagesrangesincluding: -35V to -25V,-30V to -20V, -25V to -15V,and -20V to -
10V. Unlike the positive voltages,the negative voltagesdidnotcreate all 11 lines.Asshowninfigure 15,
manyof the linesare missingorare onlypartiallywritten.Some linesseemtobe skippedoverbythe
tip. The dots on the sample’ssurface affectthe heightandwidthof the linesthatare drawn.
Figure 15: Example imagesof negative tipvoltageslinepatternsonsample 39(225 mTorr)
(a) -20V to -10V linepattern (b) -30V to -20V linepattern (c) -35V to -25V linepattern
As seeninthe previoussection,positivetipvoltagesproducedall 11lineseventhoughthe lines
couldbe veryfaintand small.There islikelysomereactionthatoccursonlywith negative voltages and
preventsthe linesfrombeingdrawn. Althoughmanylinesare missingImeasuredthe heightandwidth
of all the linesthatwere written.
0
0.2
0.4
0.6
0.8
1
1.2
5 10 15 20 25 30 35
AverageLineWidth(µm)
Voltage (V)
LBMO-STO-39 Positive Tip Voltages vs. Average Line
Width

16. Figure 16: Negative tipvoltagesvs.average line heightwithstandarddeviationbars
Negative voltagespatternshave athresholdof -16V anda saturationheightof 11.6 nm at -34V.
Most of the line widthsforthe negative voltage linesare inthe 0.6 µm to 0.7 µm range. The smallest
line widthis0.403 µm at -11V and the largestwidthis1.15 µm at -29V.
Figure 17: Negative tipvoltagesvs.average line width withstandarddeviationbars
Pattern Relaxation and Surface Aging on Sample 39 (225 mTorr)
I performedrelaxationtestsonbothpositive andnegativelinepatterns. After72 hours,the
positive voltagepatterngrewveryslightlywhilethe negative voltagepatternsstayedat the same
height.Ididnot see anypatternrelaxationonsample 39. Althoughsample 39was made inNovember
2013, I wasstill able towrite onthe sample inMay 2014. Unlike sample’s34and 37, sample 39’s age did
not affectthe abilitytowrite line patternsonit. Thatresultmay change as sample 39 agesfurther.
0
2
4
6
8
10
12
-35 -30 -25 -20 -15
LineHeight(nm)
Appplied Tip Voltage (V)
LBMO-STO-39 Negative Tip Voltages vs. Average Line
Height
0
0.5
1
1.5
-35 -33 -31 -29 -27 -25 -23 -21 -19 -17 -15
AverageLinewidth(µm)
Voltage (V)
LBMO-STO-39 Negative Tip Voltages vs. Average
Line Width

17. Sample 39 (225 mTorr) Conclusions
Sample 39 is coveredindotsand growths.The dotshindered andprevented the creationof line
patternson the sample.The line patternsthatwere createdare of low qualitycomparedtothe patterns
on samples 34 and 37. Cleanersurfacesare mucheasiertowrite on and produce betterresults.Overall
225 mTorr isnot a good growthpressure touse whencreatingLBMO samples fornanolithography.
100 mTorr sample, LBMO-STO-43
Sample LBMO-STO-43was createdon April 8,2014 witha growthpressure of 100 mTorr. I
createda 100 mTorr sample inorderto try to findthe point whenwritingwithnegativevoltages
becomespossible. Negative voltagepatternscanbe writtenon225 mTorr and 400 mTorr samplesbut
not 50 mTorr ones. There islikelyacertainpressure level abovewhichnegative voltage linescanbe
written.
Positive Applied Tip Voltages on Sample 43 (100 mTorr)
Sample 43 is significantlyrougherthansample 34 (50 mTorr),butit doesnot have anydots on
itssurface like sample 37 (225 mTorr). Despite the roughsurface Iwas still able towrite positivevoltage
line patternsasseeninFigure 18. I usedthe writingparameters thatIusedon the othersamplesformy
sample 43 tests.I wrote linespatternsinthe followingvoltage ranges:5V to15V, 10V to 20V, 15V to
25V, and 20V to 30V.
Figure 18: Example imagesof positive tipvoltagesline patternsonsample 43(100 mTorr)
(a) 5V to 15V linepattern (b) 10V to 20V linepattern (c) 20V to 30V linepattern
From image (a) sample 43 has 7V thresholdvoltage forpositive voltage line patterns. The line
patternson sample 43 are faintanduneven.Some linesare largerthanthe restof the patternas shown
inimage (c).Thisusuallyoccurswhenthe tipvoltage is20V or larger. Sample 43’sline patternsare not
as cleanand well-drawnassample 34’spatternsbuttheyare clearerthan sample 37’spatterns. Like the
previoussamples,Imeasuredthe heightandwidthof eachline andaveragedtogetherthe results.

18. Figure 19: Positive tipvoltagesvs.average line heightwithstandarddeviationbars
Unlike sample 34 (50 mTorr),sample 43 has a saturationheightof approximately7nm on the
29V line. Mostof the line heightsare between1.5nm and 4 nm. There are a few large lineslikeinFigure
18 (c) thatare increasingthe averagesof certainvoltage lines.The 20V and 28V lineshave large
standarddeviationsdue toafewlarge lines.The large linesare drawnrandomlyinthe pattern. Asseen
inFigure 20, mostof the line widthsare between0.6µm and 0.9 µm. The largestline widthis1.11 µm at
the 30V line whilethe smallestis0.571 µm at the 9V line.
Figure 20: Positive tipvoltagesvs.average line widthwithstandarddeviationbars
Negative Applied Tip Voltages on Sample 43 (100 mTorr)
I was notable to write withnegative tipvoltagesonsample 43.Applyinganegative tipvoltage
alwaysresultsina large growth. Figure 21 showsthree examplesof massive growths. Icreatedthese
growthswith70% humidityand1.6 µm/swritingspeed.
0
0.2
0.4
0.6
0.8
1
1.2
5 10 15 20 25 30
AverageLineWidth(µm)
Voltage (V)
LBMO-STO-43 Positive Tip Voltages vs. Average
Line Width
0
2
4
6
8
5 10 15 20 25 30
AverageLineHeight(nm)
Voltage (V)
LBMO-STO-43 Positive Tip Voltages vs. Average Line
Height

19. Figure 21: Example imagesof negative tipvoltageslinepatternsonsample 43(100 mTorr)
(a) -10V growth (b) -15V growth (c) -30V growth
Each growth haspointsthat are over1 µm tall.The growthsare large enoughto be seenonthe
TV monitorthatis attachedto the AFM. I triedto preventgrowthsfromformingbywritingwithalower
humidity. HoweverIwasunable togetany writingorreactionwhen I applieda-10V tipvoltage with
40% humidity tosample 43.The humiditywaslikelytoolow foranyreactiontohappen. I alsotriedto
write witha verylowvoltage and 70% humidity. Iapplieda-5V tipvoltage tosample 43 with70%
humiditybutIwas unable togetany linestoform.The voltage waslikely below the sample’sthreshold
voltage. Itmay notbe positive towrite withnegativetipvoltagesona100 mTorr sample.
Pattern Relaxation and Surface Aging on Sample 43 (100 mTorr)
I performedrelaxationtestsonsample 43withpositive tipvoltages.Iwrote a20V to 30V line
patternon sample 43 and thenwaited72 hours toscan it again.After72 hoursthere was nonoticeable
change in the line pattern. The line heightsdidnotundergoanyrelaxation. Sample43was createdon
April 8, 2014. The sample islikelynotoldenoughforage to affectthe abilitytowrite line patternson
the surface.
Sample 43 (100 mTorr) Conclusions
Positive tipvoltagesproduce faintbutcomplete linepatternsonsample 43.More advanced
nanolithographypatternscouldbe createdwithpositive voltages. Incontrast,negative voltages produce
massive growths onsample 43. I have discoveredthata100 mTorr growthpressure will notcreate a
sample thatcan be writtenon withnegative voltages.A 200 mTorr pressure like sample39 mightwork.
Overall Conclusions
I was able tocreate line patternswithpositivevoltagesonall fourof my LBMO samples. The 50
mTorr sample 34 producedthe bestline patternswhile the 225 mTorr sample 39 producedthe worst
patterns.The line patternsonsamples37 (400 mTorr) and 43 (100 mTorr) are roughand blurrybut
clearlyvisible. Sample 34(50 mTorr) was unique amongmyfoursamplesbecause itdidnothave a
saturationheight.Sample 34’sline heightsincreasedlinearlywiththe appliedpositive tipvoltages.The

20. otherthree samplesall hadsaturationheightsatveryhighvoltages.Sample34’slackof a saturation
heightmaybe due to its lowgrowthpressure and oxygenconcentration.
I have successfullywrittenonLBMOwithnegative tipvoltages.Ihave discoveredthat the
growthpressure usedduringpulsedlaserdeposition candeterminewhetherwritingonasample with
negative voltages ispossible. Thereis acertaingrowthpressure above whichnegativelinepatternscan
be writtenonLBMO. Thisgrowth pressure isapproximately 200 mTorr. Applyinganegative voltage toa
sample thatwas createdat lessthan200 mTorr pressure will cause amassive growthtoform. The
difference inresultsmaybe due tothe sample’soxygenconcentrationwhichisdeterminedbythe
sample’sgrowthpressure. Highgrowthpressurescreate alarge oxygenconcentrationinthe sample.
Overall,more researchisneededtodetermine exactlywhythe massivegrowthsoccur.
References
1) Li, R-W.(2009) ‘AFMlithographyandfabricationof multifunctionalnanostructureswithperovskite
oxides’, Int.J.Nanotechnol.,Vol.6,No.12, pp. 1067-1085.
Sample Data Table: LBMO-STO-37 (400 mTorr) Positive voltagedata
LBMO-STO-37 Positive Tip Voltages
400 mTorr Sample Line Heights (nm) in cells
Line Heights Dates, Test Number, and Line Type
September 25 September 27 September 27 November 8 September 9 September 30 September 30 September 30 September 30
Standard Test 5 Test 6 Test 7 Test 15 Test 2 Test 8 Test 9 Test 10 Test 11
Voltage (V) Average (nm) Deviation Decent Lines Decent Lines Faint Lines Decent Lines Faint Lines Faint Lines Blurry Lines Decent Lines Rough Lines
10 3.06 0.113137085 No Line 2.98 3.14
11 2.6767 0.30892286 2.62 2.40 3.01
12 2.4167 0.387341365 1.97 2.62 2.66
13 2.5333 0.270246801 2.84 2.43 2.33
14 2.6333 0.37072002 2.66 2.99 2.25
15 2.925 0.772765596 2.42 3.36 2.14 3.78
16 3.095 1.234868414 2.72 2.82 1.98 4.86
17 3.175 1.27039364 3.44 2.68 1.79 4.79
18 3.2725 1.168799241 3.10 2.90 2.17 4.92
19 2.8375 1.263576274 2.17 2.88 1.71 4.59
20 2.6314 0.851046974 2.51 2.81 2.16 4.41 2.29 1.75 2.49
21 2.505 1.539274721 4.81 1.86 1.65 1.70
22 2.24 0.697471624 2.46 3.05 1.39 2.06
23 2.29 1.284653001 4.10 2.31 1.37 1.38
24 2.46 1.386755806 4.52 1.72 1.56 2.05
25 2.59 0.836953802 3.77 1.92 2.08 2.58
26 2.5867 1.046438404 3.33 1.39 3.04
27 2.5767 1.127578526 3.50 1.32 2.91
28 3.12 0.340734501 3.51 2.88 2.97
29 2.9467 0.920452787 3.85 2.98 2.01
30 3.748 1.076229529 3.72 2.01 4.74 4.54 3.73
31 3.56 0.183847763 3.43 3.69
32 3.975 0.403050865 4.26 3.69
33 4.105 0.572756493 3.70 4.51
34 4.015 0.643467171 3.56 4.47
35 3.825 0.714177849 3.32 4.33
36 4.115 0.374766594 3.85 4.38
37 4.195 0.106066017 4.27 4.12
38 4.18 0.410121933 3.89 4.47
39 4.44 0.254558441 4.62 4.26
40 4.32 0.692964646 3.83 4.81