Ion beam can create self-organised nanostructures. e. nanripples and nanodots

1. Differential sputtering yields and diffusivities leads both
topography and composition variation for binary
compound [3].
𝝏𝒉
𝝏𝒕
= −𝜴 𝑭 𝑨 + 𝜵. 𝑱 𝑨 + 𝑭 𝑩 + 𝜵. 𝑱 𝑩 𝐭𝐨𝐩𝐨𝐠𝐫𝐚𝐩𝐡𝐢𝐜
∆
𝝏𝒄 𝒔
𝝏𝒕
= 𝛀 𝒄 𝒃 − 𝟏 𝑭 𝑨 + 𝜵. 𝑱 𝑨 + 𝒄 𝒃 𝑭 𝑩 + 𝜵. 𝑱 𝑩 𝐜𝐨𝐦𝐩𝐨𝐬𝐢𝐭𝐢𝐨𝐧𝐚𝐥
𝑱𝒊 = −𝑫𝒊 𝒏 𝒔 𝜵𝑐 𝑠 𝒊
+
𝑫𝒊 𝑐 𝑠 𝒊 𝒏𝜴𝜸
𝒌 𝑩 𝑻
𝜵𝜵 𝟐 𝐡 − 𝝁𝒊 𝜵𝒉 , 𝐢 = 𝐀, 𝐁
Surface atomic current
Transitional morphology in binary alloy nanopatterning via ion beams
Basanta Kumar Parida and Subhendu Sarkar*
Dept. of Physics, Indian Institute of Technology(IIT), Ropar, Punjab, India-140001
Ion beam sputtering (IBS) of crystalline or amorphous materials
spontaneously results in nanoscale ripples or dots in self-organizing
manner[1-2].
Ripple wavelength of ripples depend on angle of ion incidence,
temperature, ion flux, fluence, ion mass etc.
IBS is a single step process for large area patterning, faster and cheaper
as compared to other lithographic techniques.
Nanopatterns are used for microelectronic devices, template surface
and optical studies.
Curvature dependent sputtering (roughens) and thermal surface
diffusion (smoothens) compete to create nanoscale pattern.
𝝏𝒉
𝝏𝒕
= −𝒗 𝟎 + 𝜸 𝒙
𝝏𝒉
𝝏𝒙
+ 𝝑 𝒙
𝝏 𝟐 𝒉
𝝏𝒙 𝟐
+ 𝝑 𝒚
𝝏 𝟐 𝒉
𝝏𝒚 𝟐
− 𝑩𝛁 𝟐 𝛁 𝟐 𝒉
Metal-semiconductor system (CoSi) far from 50:50 surface
and bulk composition were chosen.
Highly ordered defect-free ripples can be produced by ion
bombardment of a binary material if the ion species, energy
and angle of incidence are appropriately chosen[3].
Introduction
Ar+  Si 500 eV, 67o
Normal ion incidence or oblique incidence with sample rotation of
binary compounds gives nanodots with hexagonal ordering and also
adding metal impurity results in nanodots and nanoripples.
𝝏𝒉
𝝏𝒕
= −𝜴 𝑭 𝑨 + 𝜵. 𝑱 𝑨 + 𝑭 𝑩 + 𝜵. 𝑱 𝑩 𝐭𝐨𝐩𝐨𝐠𝐫𝐚𝐩𝐡𝐢𝐜
∆
𝝏𝒄 𝒔
𝝏𝒕
= 𝛀 𝒄 𝒃 − 𝟏 𝑭 𝑨 + 𝜵. 𝑱 𝑨 + 𝒄 𝒃 𝑭 𝑩 + 𝜵. 𝑱 𝑩 𝐜𝐨𝐦𝐩𝐨𝐬𝐢𝐭𝐢𝐨𝐧𝐚𝐥
𝑱𝒊 = −𝑫𝒊 𝒏 𝒔 𝜵𝑐 𝑠 𝒊 +
𝑫𝒊 𝑐 𝑠 𝒊
𝒏𝜴𝜸
𝒌 𝑩 𝑻
𝜵𝜵 𝟐
𝐡 − 𝝁𝒊 𝜵𝒉 , 𝐢 = 𝐀, 𝐁
Binary compound system
Theoretical background
Motivation
CoxSi1-x thin film growth Ion irradiation
Morphology transition from 500eV to 1200 eV. Surface
roughens with energy increment.
Elongated semi-ellipsoid like structures at higher energies
of 1000, 1200 eV.
Wavelength obeys a power law
𝑓0.123
where 𝑓 is the fluence.
Roughness increases exponentially
with the fluence.
Single elemental system
Methodology
Energy variation
Fluence variation
Composition variation
Angle variation
-20 -10 0 10 20
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
Current(A)
Voltage (V)
pristine
10 min
15 min
30 min
45 min
60 min
ion beam direction measurement
Higher ordered ripples
Nano cauliflower
Rocking Substrate
Acknowledgement
MHRD for fellowship and DST for project funding
[1] Sarkar et. al. New. J. Phys. 10, 083012. (2008) [2] Garcia et. al. Mat. Sci. Eng. Rep. 86, 1(2014) [3]Shenoy et.al. Phys. Rev. Lett. 98, 256101 (2007) [4] Motta J. Phys. D: Appl. Phys. 45, 122001 (2012)[5] Chan et.al. J Appl. Phys. 101, 121301(2007)