STRUCTRAL, ELECTRICAL AND THERMOELECTRIC PROPORTIES OF        CrSi2 THIN FILMS                    by          Makram Abd E...
 Thermoelectric Materials and Application         Clean source of energy – Power generation upon application of heat grad...
 Thermoelectric phenomena and coefficients         In Solid state thermoelectric devices         Diffusion Principle in ...
 Background and Thermoelectric Phenomena    1. Approximately 90% of the world’s electricity is produced by heat energy   ...
Transition           Potential thermoelectric materials                         metal silicides                      CrSi...
The issueThe electrical and thermal properties of a material are determined by the same crystaland electronic structure  ...
Literature data on CrSi2Physical property                                    ValueEnergy gap                             ...
Outline    PART 1    Thin Film Preparation - Experiments on Thin Film samples              Thin film processing         ...
Thin film processing quartz glass substrates( κ=1.38W/mK, R=1018Ωm) were prepared by:Aquasonic deionized water bath, meth...
Sputtering Process chamber                             Dept. of Electrical and Computer Engineering10                    ...
Thin film thickness measurement     Surface Profiler Veeco Dektak 6M Stylus Profilometer                                 ...
Thin film annealing      In order to find out the effect of temperature, the thin film samples were     annealed under a...
Thin film - Compositional Analysis       The compositions of processed thin filmsamples were verified by      performing ...
Thin film microstructure images-Scanning Electron Microscope (SEM)     0.1 µm thin film as sputtered                     ...
Thin film – Structural Analysis X-ray diffraction pattern were taken using a Bruker-AXS D8 Vario Advance using a Johansso...
Thin film structural analysisThe obtained results from the Rietveld refinement for all samples regarding their            ...
Thin film structural analysis               X-ray diffraction refinement values for CrSi2 0.1 µm thin films              S...
Thin film structural analysis- diffraction patterns  1µm thin film- 1 hour annealing time- 300˚C-                 1µm thin...
Thin film structural analysis- diffraction patterns  0.1µm thin film- 1 hour annealing time-                 0.1µm thin fi...
Seebeck coefficient measurementSeebeck voltages of 1µm and 0.1µm thin films were measured for various annealingtemperatu...
Seebeck coefficient results                           90      Seebeck coeffcient                           80            ...
1d2          Seebeck coefficient discussion     Seebeck coefficients in general increase with the annealing temperature ...
Thin Film resistivity measurement Resistivity of 1µm and 0.1µm thin films for various annealing temperatures in the rang...
Thin Film resistivity results                            1                           0.9                           0.8   ...
Thin Film resistivity resultsResistivity of 1µm thin films couldn’t be measured due to their high resistance valueswhich...
Thermoelectric power factor measurement The thermoelectric power factors, P, of 0.1µm thin films was calculated and plot...
Thermoelectric power factor results                           1.20E-03     Power Factor ( W/K2                           ...
 PART 1-Results and discussion Seebeck coefficient and resistivity increases linearly, between 100˚C to 300˚C this corre...
 PART 1- Results and discussion0.1 µm thin film showing a plateau beyond the transition temperature and 1 µm thin filmsh...
Results and discussion Due to highly resistive nature of 1 µm thin films, the thermoelectric power factor forthese films...
PART 2-Design of Three Gun Sputtering System                                     Investigate ternary                     ...
Design of Three Gun Sputtering System                  Heating              99% pure                   High vacuum       ...
Design of Three Gun Sputtering System                Three gun sputtering system building blocks:                 Oil se...
Design of Three Gun Sputtering SystemSolid works design A drawing of the stainless steel 6 way                          ...
Design of Three Gun Sputtering SystemSolid works design                    A schematic diagram illustrating the focus of...
Design of Three Gun Sputtering SystemSystem assembly                          A photograph showing the three gun sputter...
Design of Three Gun Sputtering System                  photograph showing an inside look of the chamber37                ...
Design of Three Gun Sputtering System                  A symbol representation of the 3 gun sputtering system38          ...
Three gun sputtering system results Residual gas analyzer resultsThe quadrupole gas analyzer spectras are plots of       ...
Three gun sputtering system results     Before (Yellow) and after (Green) RGA spectrum showing effect of reducing the     ...
Three gun sputtering system results       Quadrupole gas analyzer spectrum of        ratio versus partial pressure-       ...
PART 2- Results and discussion       In order a deposit ternary and higher order alloys, a three gun sputtering      syst...
ConclusionCrSi2 films of two different thicknesses were prepared by rf sputtering.As deposited and annealed (300˚C to 6...
Recommendation and Future workBased on our experience with CrSi2 deposition and characterization, and also the designand ...
Acknowledgment              Committee members:                                    Dr. Rama Venkat                        ...
I would like to thank the following companies on their support for making the design of the 3     gun sputtering system po...
THANK YOU ALL       Dept. of Electrical and Computer Engineering47           University of Nevada, Las Vegas
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Makram thesis presentation

  1. 1. STRUCTRAL, ELECTRICAL AND THERMOELECTRIC PROPORTIES OF CrSi2 THIN FILMS by Makram Abd El QaderCandidate for Master of Science in Electrical Engineering Department of Electrical and Computer Engineering Department
  2. 2.  Thermoelectric Materials and Application Clean source of energy – Power generation upon application of heat gradient (a) (b) PN couple used as TEG (a)-Seebeck effect, and TEC (b)- Peltier effect Dept. of Electrical and Computer Engineering2 University of Nevada, Las Vegas
  3. 3.  Thermoelectric phenomena and coefficients  In Solid state thermoelectric devices Diffusion Principle in materials Mobile charge carriers Thermal gradient Charge build up (e-) & (h+) Electrostatic potential (voltage) Seebeck effect- thermoelectric generation (TEG)  The efficiency of power generation in thermoelectric devices is determined by its dimensionless figure of merit (ZT): ZT=α2σ/κ α is the Seebeck coefficient µV/K, σ is the electrical conductivity Ωm, and κ is the thermal conductivity W/m-K.  The thermoelectric performance can also be evaluated by the power factor P=α2/ρ ρ is the resistivity Ωm Dept. of Electrical and Computer Engineering3 University of Nevada, Las Vegas
  4. 4.  Background and Thermoelectric Phenomena 1. Approximately 90% of the world’s electricity is produced by heat energy as a result of burning fossil fuel 2. Production plants typically operate at 30-40 per cent efficiency, loosing around 15 terawatts of power in the form of heat to the environment. 3. Waste Heat sources are found almost in every process and electronic devices (Residential heating, automotive exhaust, and industrial processes 4. Thermoelectric power generators can convert some of this waste heat into useful power 5. Thermoelectric devices are potential power source due to their direct conversion of thermal gradients into electric current. 6. Electronic devices, International space station and Satellites, Automobile companies, Power plants Dept. of Electrical and Computer Engineering4 University of Nevada, Las Vegas
  5. 5. Transition  Potential thermoelectric materials metal silicides CrSi2, FeSi2, CoSi2,…. … Characteristics of Silicides  Partially filled d- orbitals- Seebeck value much higher  High melting point and chemical stability at high temperatures  Relatively low thermal conductivity values  Materials with highest figure of merit A good thermoelectric material should BiT2 and SbTe hold the highest ZT values of 3 have low electrical resistivity, low thermal conductivity, and a large Seebeck coefficient. Dept. of Electrical and Computer Engineering 5 University of Nevada, Las Vegas
  6. 6. The issueThe electrical and thermal properties of a material are determined by the same crystaland electronic structure Usually:They cannot be controlled independently. The challenge is to find ways to decouple theelectrical and thermal properties keys:Study thermoelectric materials in Thin Film form. This may cause a change in thematerial thermal and electrical properties 2-D dimensions Precise controlled composition Easy to create defects-doping, process conditions.. Scalable for small/large devices Theoretical studies predict better enhanced ZT with low dimensional structures. Motivation Study the structural, electrical, and thermoelectric properties of CrSi2 thin films to better enhance the ZT. Dept. of Electrical and Computer Engineering 6 University of Nevada, Las Vegas
  7. 7. Literature data on CrSi2Physical property ValueEnergy gap indirect band gap 2.7eVCarrier type P type 4×109 cm3Bulk electrical resistivity at (RT) 0.9 mΩcmBulk Seebeck coefficient at (RT) 96µV/KBulk thermal conductivity at (RT) 10W/mKThin film crystallization temperature 300˚CCrystal structure Hexagonal structureSpace group P6222Lattice parameters a= b= 4.4220Å, c=6.351Å Structural, thermal, and electrical properties of bulk CrSi2 are well studied.” “Structural, thermal, and electrical properties of CrSi2”, by T. Dasgupta, J. Etourneau,.”  electrical and structural properties of ( 50nm) thin film of sputtered CrSi2” Electrical and structural properties of thin films of sputtered CrSi2”, by S.F. Gong a, X.-H. Li a..” Electrical, structural, and transport properties of CrSi2/ Si (111) Dept. of Electrical and Computer Engineering7 University of Nevada, Las Vegas
  8. 8. Outline PART 1 Thin Film Preparation - Experiments on Thin Film samples  Thin film processing Energy Dispersive X-ray diffraction (EDAX)  X-ray Diffraction (XRD)  Four probe point resistivity measurement Seebeck coefficient measurement Power factor measurement Results and discussion drawn on thin film samples PART 2 Design and assembly of three gun sputtering system  Design motivation  Design methodology Results and discussion drawn from system pump down  Final conclusions and Future work Dept. of Electrical and Computer Engineering8 University of Nevada, Las Vegas
  9. 9. Thin film processing quartz glass substrates( κ=1.38W/mK, R=1018Ωm) were prepared by:Aquasonic deionized water bath, methyl alcohol, dried out with nitrogengas, and heated. 1µm and 0.1µm CrSi2 thin films were prepared by RF sputteringProcess condition ValueBase pressure (torr) 1.2×10-7Ar gas pressure (mtorr) 1RF power supplied (W) 200Target substrate 3distance (inch)Pre- sputtering time 10(min)Deposition time (min) 7 min for 0.1µm, 37min for 1µm Dept. of Electrical and Computer Engineering9 University of Nevada, Las Vegas
  10. 10. Sputtering Process chamber Dept. of Electrical and Computer Engineering10 University of Nevada, Las Vegas
  11. 11. Thin film thickness measurement Surface Profiler Veeco Dektak 6M Stylus Profilometer The obtained thin films have a step profile similar to the one show below Deposition TimeS.No Thickness (µm) Deposited CrSi2 material (min) Glass substrate Step Profile 1. 5 0.08 2 10 0.12 3 30 0.75 4 45 1.2 5 60 1.4 Dept. of Electrical and Computer Engineering11 University of Nevada, Las Vegas
  12. 12. Thin film annealing  In order to find out the effect of temperature, the thin film samples were annealed under argon gas (Ar) ambience.  Annealing Temperature (T) = 300˚C, 400 ˚C, 500 ˚C, 600 ˚C  Argon gas Pressure (P) = 695 torr  Duration time (t) = 60 and 120 minutes Dept. of Electrical and Computer Engineering12 University of Nevada, Las Vegas
  13. 13. Thin film - Compositional Analysis  The compositions of processed thin filmsamples were verified by performing Energy Dispersive X-ray Analysis (EDAX).  JOEL JSM – 5600 Scanning Electron Microscope, Energy = 15keV Thin film samples with 0.1µm thickness have shown an atomic composition of Cr=37.64% and Si=62.36%.  Thin films samples with 1µm thickness have shown an atomic composition of Cr=39.27% and Si=60.73% The obtained results show that the discrepancy between the compositions of the target material and thin films are less than 5%. Dept. of Electrical and Computer Engineering13 University of Nevada, Las Vegas
  14. 14. Thin film microstructure images-Scanning Electron Microscope (SEM) 0.1 µm thin film as sputtered 0.1 µm thin film after annealing at 300˚C 1 µm thin film as sputtered 1 µm thin film after annealing at 300˚C14 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  15. 15. Thin film – Structural Analysis X-ray diffraction pattern were taken using a Bruker-AXS D8 Vario Advance using a Johansson-type primary monochromator with Cu kα1 emission λ=1.54063Å Incident beam angle θ= 5˚ Reflected angle 2θ=10-90˚The Rietveld structure refinement allows peaksfitting by calculating the structure factors foreach lattice plane by applying :pseudo-Voigt type profile functions (Thompson-Cox-Hastings) fundamental parameter approach. Dept. of Electrical and Computer Engineering15 University of Nevada, Las Vegas
  16. 16. Thin film structural analysisThe obtained results from the Rietveld refinement for all samples regarding their X-ray diffraction refinement values for CrSi2 1µm thin films Sample ID R-Bragg Scaling Factor Refined cell Refinement parameters, a and c Residual (<< 5%) (Å)  Bragg residuals: indicates the difference CriS2 as-sputtered NA NA NA between the calculated and 1.103 4.449, 6.293 CriS2 300C 1h 0.000209 measured intensities 4.4331, 6.317 Scaling factor: gives an CriS2 400C 1h 1.292 0.000235 indication about amount of 4.4152, 6.3359 CriS2 500C 1h 1.705 0.0001637 the phase in the material 4.443, 6.244 The refined lattice CriS2 600C 1h 1.309 0.000280 parameters 1.249 4.445, 6.285 CriS2 300C 2h 0.000258 4.4289, 6.304 CriS2 400c 2h 1.353 0.000299 1.891 4.4127, 6.3382 CriS2 500c 2h 0.0002248 4.4304, 6.2981 CriS2 600C 2h 1.388 0.0002750 Dept. of Electrical and Computer Engineering 16 University of Nevada, Las Vegas
  17. 17. Thin film structural analysis X-ray diffraction refinement values for CrSi2 0.1 µm thin films Sample ID R-Bragg Refinement Scaling Factor Refined cell Residual (<< 5%) parameters, a and c (Å) NA NA CriS2 as-sputtered NA 0.646 4.438, 6.280 CriS2 300C 1h 0.000219 4.439, 6.253 CriS2 400C 1h 0.814 0.000265 4.425, 6.262 CriS2 500C 1h 0.625 0.000264 4.435, 6.272 CriS2 600C 1h 0.538 0.000452 0.512 4.420, 6.286 CriS2 300C 2h 0.000193 CriS2 400c 2h 0.602 0.000263 4.433, 6.260 0.581 4.423, 6.265 CriS2 500c 2h 0.000225 0.691 4.439, 6.271 CriS2 600C 2h 0.000234R-Bragg Refinement Residual much less than 5%, thus fit is excellent. lattice parametersobtained for various thin films are in the within the expected values for CrSi2. Dept. of Electrical and Computer Engineering17 University of Nevada, Las Vegas
  18. 18. Thin film structural analysis- diffraction patterns 1µm thin film- 1 hour annealing time- 300˚C- 1µm thin film- 2 hour annealing time- 600˚C 300˚C- 600˚CCrystallization of the hexagonal modification The diffraction pattern for 1 hr. is dominatedof CrSi2 was observed at 300˚C by the (111) and (112) peak intensities, and forCrystallization became better at higher 2 hr. is dominated by the (111),(112), and (003)annealing temperatures. peak intensities. Dept. of Electrical and Computer Engineering 18 University of Nevada, Las Vegas
  19. 19. Thin film structural analysis- diffraction patterns 0.1µm thin film- 1 hour annealing time- 0.1µm thin film-2 hour annealing time- 300˚C- 600˚C 300˚C- 600˚CCrystallization of the hexagonal modification There is no change in the peak intensitiesof CrSi2 was observed at 300˚C between 1 hr. and in the 2 hr. annealed samplesCrystallization became better at higher This indicates that 0.1µm CrSi2 thin films areannealing temperatures. fully crystallized at 1 hr. Dept. of Electrical and Computer Engineering 19 University of Nevada, Las Vegas
  20. 20. Seebeck coefficient measurementSeebeck voltages of 1µm and 0.1µm thin films were measured for various annealingtemperatures in the range of 100˚C-600˚C for two different annealing times, 1hr and 2 hr.A Seebeck voltage measurement device was designed and built to measure the Seebeckcoefficient of the CrSi2 films at room temperatureThe estimated accuracy of the seebeck coefficient measured was ±5%, and was verified bymeasuring the Seebeck coefficient of Ni samples in both bulk and thin Film form withknown Seebeck coefficient values Seebeck coefficient measurement apparatus at 20˚C ΔT Dept. of Electrical and Computer Engineering20 University of Nevada, Las Vegas
  21. 21. Seebeck coefficient results 90 Seebeck coeffcient 80 70 60 1µm thin film (µV/K) 50 40 Seebeck coefficient (µV/K)-1hr 30 annealing 20 Seebeck coefficient (µV/K)-2 hr 10 annealing 0 0 200 400 600 800 Annealing temperatures(C˚) 70 Seebeck coeffcient 60 0.1µm thin film 50 40 (µV/K) 30 Seebeck coefficient (µV/K)-1hr 20 annealing 10 Seebeck coefficient (µV/K)-2 hr 0 annealing 0 100 200 300 400 500 600 700 Annealing temperatures(C˚) Dept. of Electrical and Computer Engineering21 University of Nevada, Las Vegas
  22. 22. 1d2 Seebeck coefficient discussion Seebeck coefficients in general increase with the annealing temperature for both thicknesses and annealing times up to 400oC. This behavior is directly related to the better crystallinity of the thin films at higher annealing temperatures. In the temperature range of 400 to 500oC, all plots show a sudden change in Seebeck coefficient Seebeck coefficient saturates at around 60µV/K for 0.1 µm thin films .For 1 µm thin films annealed for 1 hr. the Seebeck coefficient shows a plateau between 400 and 500oC and then increases and reaches 81µV/K close to the reported bulk value of 96µV/K, whereas the 2 hr. annealed thin film shows a decrease This difference behavior of the 1 µm thin films can be related to the degradation of the thin film micro- structurally with the creation of voids and cracks at higher annealing temperature and longer annealing times. 22 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  23. 23. Thin Film resistivity measurement Resistivity of 1µm and 0.1µm thin films for various annealing temperatures in the range 300oC-600oC for two different annealing time, 1hr and 2hr. Four probe point resistance measurement apparatus (ASU-Newman Group) was used at room temperature Thin film resistivity values were calculated using with t is the thin film thickness s is the spacing between the probes Dept. of Electrical and Computer Engineering23 University of Nevada, Las Vegas
  24. 24. Thin Film resistivity results 1 0.9 0.8 Resistivity (mΩ-cm) 0.1µm thin film 0.7 0.6 0.5 Resistivity (mΩ-cm)- 1 0.4 hr annealing 0.3 Resistivity (mΩ-cm)- 2 hr annealing 0.2 0.1 0 0 100 200 300 400 500 600 700 Annealing temperatures(C˚) Dept. of Electrical and Computer Engineering24 University of Nevada, Las Vegas
  25. 25. Thin Film resistivity resultsResistivity of 1µm thin films couldn’t be measured due to their high resistance valueswhich exceeded the limitation of the measurement systemIt is estimated that 1µm thin films have a resistance value larger than 1MΩ. Based thisestimate, the resistivities of the annealed 1µm thin films were calculated to be larger than0.000453 MΩ-cm, while the as deposited show to have resistivity of 1.197mΩ-cm.For both annealing times, 1hr. and 2hr., 0.1 µm thin films show that the resistivityincreases with annealing temperature till 300oC and reaches a value of 0.9 mΩ-cm,which is close to the reported bulk value and then decreases till 400o C and then saturatesThe increase in resistivity is consistent with the film become more crystalline withtemperature. Decrease of resistivity beyond 400oC cannot be explained. This needs to beinvestigated further. Dept. of Electrical and Computer Engineering25 University of Nevada, Las Vegas
  26. 26. Thermoelectric power factor measurement The thermoelectric power factors, P, of 0.1µm thin films was calculated and plotted for various annealing temperatures in the range of 300˚C-600˚C for two different annealing times, 1hr. and 2 hrs. The thermoelectric power factor, P for 1µm thin films could not be calculated as resistivity, which is necessary for the calculation could not be measured due to the limitation instrument. The calculations of the power factor were done using the following equation: P=α2/ρ (W/K2 m) where α is the Seebeck coefficient ρ is the resistivity Dept. of Electrical and Computer Engineering26 University of Nevada, Las Vegas
  27. 27. Thermoelectric power factor results 1.20E-03 Power Factor ( W/K2 1.00E-03 0.1µm thin film 8.00E-04 power factor 0.1 1hour m) 6.00E-04 annealed 4.00E-04 power factor 0.1 2hour 2.00E-04 annealed 0.00E+00 0 100 200 300 400 500 600 700 Annealing temperature C˚Thermoelectric power factor increases with annealing temperature from 300oC to400oC and saturates at about 0.9 x 10-3 W/(K2.m) beyond 400oC for 0.1µm thin filmsannealed for 2 hrs0.1µm thin films annealed for 1 hr, thermoelectric power factor increases withannealing temperature from 300oC to 500oC and saturates at about 1.1 x 10-3 W/(K2.m)beyond 500oCThis behavior can be attributed to increase in crystallinity in the higher annealingtemperature range. Dept. of Electrical and Computer Engineering27 University of Nevada, Las Vegas
  28. 28.  PART 1-Results and discussion Seebeck coefficient and resistivity increases linearly, between 100˚C to 300˚C this correlates well with the observation of increased crystallinity of the deposited thin films. The difference measured Seebeck coefficients between 0.1 µm and 1 µm thin films annealed in this temperatures range is very minimal. The resistivity results show a marked difference with 0.1 µm exhibiting measurable values in the range of 0.2 to 0.9 mΩ-cm, and 1 µm thin films have resitivities larger than 0.000453 MΩ-cm This difference is related to the drastic difference in the mictrostructure between the two thicknesses. Annealed 1 µm thin films exhibit a large density of pores, where as 0.1 µm thin films exhibit a smooth texture. Both 0.1 and 1 µm thin films show a transition in Seebeck coefficient between 300oC and 400oC Dept. of Electrical and Computer Engineering28 University of Nevada, Las Vegas
  29. 29.  PART 1- Results and discussion0.1 µm thin film showing a plateau beyond the transition temperature and 1 µm thin filmshowing a plateau for about 100 C range and then increasing further for shorter anneal timesand a peak at the transition temperature for longer anneals.Degradation of properties for 1 µm thin films with longer duration of anneal may be relatedto degradation of the thin films microstructurally. In other words, cracks and voids maycause the degradation.0.1 µm thin films show a peak in resistivity around 300oCDecrease of resitivities beyond 300˚C anneal is unclear1 µm thin films have resistivity larger than the limits of the instrument. Such highresistance may be a result of porosity observed in the annealed films.Thermoelectric power factors for 0.1 µm thin films with respect to annealing temperaturesshow a behavior similar to that of Seebeck coefficients, increasing with temperature andreaching a plateau value of 1.0 x 10-3 W/(K2 m) at around 400o C to 450o C Dept. of Electrical and Computer Engineering29 University of Nevada, Las Vegas
  30. 30. Results and discussion Due to highly resistive nature of 1 µm thin films, the thermoelectric power factor forthese films has an upper estimate of 6.403×10-6 W/(K2 m) These results suggest that annealed 400˚C thin films of thicknesses in the range of0.1µm are more suitable for device applications when glass substrates are employed. Dept. of Electrical and Computer Engineering30 University of Nevada, Las Vegas
  31. 31. PART 2-Design of Three Gun Sputtering System Investigate ternary and higher order thermoelectric alloys limitation of the Better control over current sputtering process conditions ( gas system in the solid input, heat, rotation, state fabrication vacuum level, etc….) laboratory at UNLV. Design motivation Dept. of Electrical and Computer Engineering31 University of Nevada, Las Vegas
  32. 32. Design of Three Gun Sputtering System Heating 99% pure High vacuum capability for films level ( 10-9 substrate oxide sale) remove multiple target materials / DC, Deposition RF power yield monitoring Design considerations Ion beam etching and Precise inert cleaning gas control capability Dept. of Electrical and Computer Engineering32 University of Nevada, Las Vegas
  33. 33. Design of Three Gun Sputtering System Three gun sputtering system building blocks: Oil sealed rotary mechanical pump (MP) Molecular drag pump (MDP) Turbo-molecular pump CTI Cryogenic pump Vacuum process chamber Convectron gauge Ionization gauge Capacitance manometer gauge Mass flow controller Crystal thickness monitor (QCM) Substrate table- heat and rotation Residual gas analyzer (RGA) Sputter sources Ion gun Gate valves Water chiller Dept. of Electrical and Computer Engineering33 University of Nevada, Las Vegas
  34. 34. Design of Three Gun Sputtering SystemSolid works design A drawing of the stainless steel 6 way A schematic diagram showing top cross chamber flange-housing for sputter guns and shutters A schematic diagram of top flange with sputter schematic diagram of the three sputter sources-guns used sources and shutters installed Dept. of Electrical and Computer Engineering 34 University of Nevada, Las Vegas
  35. 35. Design of Three Gun Sputtering SystemSolid works design A schematic diagram illustrating the focus of the three guns to the location of the substrate A drawing of the of the deposition chamber 35 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  36. 36. Design of Three Gun Sputtering SystemSystem assembly A photograph showing the three gun sputtering system 36 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  37. 37. Design of Three Gun Sputtering System photograph showing an inside look of the chamber37 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  38. 38. Design of Three Gun Sputtering System A symbol representation of the 3 gun sputtering system38 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  39. 39. Three gun sputtering system results Residual gas analyzer resultsThe quadrupole gas analyzer spectras are plots of versus partial pressure Quadrupole gas analyzer spectrum after initial pump down It is observed from above spectra that when the system was turned on for the first time, high Nitrogen (N) at of 28 and Oxygen (O2) of 32 peaks, were observed making the vacuum level to stay in 10-05 Torr scale.39 Dept. of Electrical and Computer Engineering
  40. 40. Three gun sputtering system results Before (Yellow) and after (Green) RGA spectrum showing effect of reducing the foreline pressure of the turbopump by adding a molecular drag pump It was observed from the green RGA spectrum that the vacuum level in the chamber gets much better (10-7 torr) after solving the problem of compression ratio by installing the molecular drag pump between the turbopump and mechanical pump Dept. of Electrical and Computer Engineering40 University of Nevada, Las Vegas
  41. 41. Three gun sputtering system results Quadrupole gas analyzer spectrum of ratio versus partial pressure- At the present The system pumped overnight to the mid 10-09 Torr range, leaving the water peak of 18 as the major one as expected Dept. of Electrical and Computer Engineering41 University of Nevada, Las Vegas
  42. 42. PART 2- Results and discussion  In order a deposit ternary and higher order alloys, a three gun sputtering system was designed, built and tested for its level of vacuum levels and cleanliness.  The tests showed that the three-gun sputtering system is of vacuum levels of 10-9 torr and shows extremely low level of impurities and is ready for future sputtering works in this area. Dept. of Electrical and Computer Engineering42 University of Nevada, Las Vegas
  43. 43. ConclusionCrSi2 films of two different thicknesses were prepared by rf sputtering.As deposited and annealed (300˚C to 600˚C) were characterized for their structural,electrical, and thermoelectric transport propertiesAs-sputtered CrSi2 film is amorphous at room temperature and crystallizes around300˚C independent of thickness.The Seebeck voltage of the1µm films increase sharply with annealing temperaturesand reaches a value of 81µV/K, which close to that of bulk CrSi2, and 62µV/K for0.1µm filmsThese results suggest that annealed thin films of thicknesses in the range of 0.1µmround 400˚C are more suitable for device applications when glass substrates areemployed. Dept. of Electrical and Computer Engineering43 University of Nevada, Las Vegas
  44. 44. Recommendation and Future workBased on our experience with CrSi2 deposition and characterization, and also the designand assembly of the three gun sputtering system, the following issues are recommendedfor future investigation:Investigation of the structural behavior of the 1µm CrSi2 thin films at annealingtemperatures greater than 300C. In other words, identify the reasons for the film to crackwith annealing.Study of the electrical and thermoelectric properties as a function of thin filmcomposition before and after annealing.Measurement of the thermal conductivity of all deposited thin films before and afterannealing, to allow us calculate the thermoelectric figure of merit ZT.Use of the designed three gun sputtering system to better sputter CrSi2 thin films.44 Dept. of Electrical and Computer Engineering University of Nevada, Las Vegas
  45. 45. Acknowledgment Committee members: Dr. Rama Venkat Dr. Ravhi Kumar Dr. Thomas Hartmann Dr. Nathan Newman Group members: Stan Goldfarb Dr.Paolo Ginobbi Brandon blackstone Nirup Bandaru Jorge Reynaga Eric Knight Mike Shappie Friends and family: I would like to thank my parents, my family, and my freinds for their great support. I would like to thank my brothers Charbel Azzi and Charles Azzi on their great support too. Dept. of Electrical and Computer Engineering45 University of Nevada, Las Vegas
  46. 46. I would like to thank the following companies on their support for making the design of the 3 gun sputtering system possible: Engineering college-Electrical and computer engineering Department College of sciences- Physics Dept- High pressure center UNLV Graduate College Ron Powell; Novellus Steve Schwartz and Steven Michaud; Brooks Automation Dan Watt John Brooks and Tom Bogdan; MDC; Fred Van der Linde Chris Malocsay; Semicore Craig Hall; Ferrofluidics Paul Becker; Fil-Tech Dave Mahoney; Rigaku Neil Peacock and Dick Jacobs; MKS Richard Osburn NCCAVS Doug Schatz; Advanced Energy Ralph Brogan; Pumps International Mark Bernick; Angstrom Sciences Mike Ackeret; Transfer Engineering Don Sarrach; Plasmaterials Neal Ely; Las Positas College Todd Johnson and Harry Grover; MeiVac Larry Lu; CLuLab Will Hale; AJA International Mark Bernick; Angstrom Sciences Dept. of Electrical and Computer Engineering46 University of Nevada, Las Vegas
  47. 47. THANK YOU ALL Dept. of Electrical and Computer Engineering47 University of Nevada, Las Vegas

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