Real Time Spectroscopic Ellipsometry Analysis of First Stage CuIn1−xGaxSe2 Growth: Indium-Gallium Selenide Co-Evaporation

Autor: Randy J. Ellingson, Prakash Koirala, Robert W. Collins, Michael J. Heben, Khagendra P. Bhandari, Sylvain Marsillac, Nikolas J. Podraza, Geethika K. Liyanage, Abdel-Rahman Ibdah, Puruswottam Aryal, Dinesh Attygalle, Puja Pradhan, Jian Li
Jazyk: angličtina
Rok vydání: 2018
Předmět:
Materials science
thickness measurement
photovoltaic cells
chemistry.chemical_element
02 engineering and technology
Substrate (electronics)
01 natural sciences
lcsh:Technology
Article
real time analysis
spectroscopic ellipsometry
0103 physical sciences
Surface roughness
Deposition (phase transition)
complex dielectric function
General Materials Science
III2-VI3 semiconductor materials
Thin film
lcsh:Microscopy
lcsh:QC120-168.85
010302 applied physics
lcsh:QH201-278.5
business.industry
lcsh:T
compositional analysis
CuIn1−xGaxSe2
021001 nanoscience & nanotechnology
Evaporation (deposition)
Copper indium gallium selenide solar cells
chemistry
lcsh:TA1-2040
Optoelectronics
lcsh:Descriptive and experimental mechanics
lcsh:Electrical engineering. Electronics. Nuclear engineering
0210 nano-technology
business
lcsh:Engineering (General). Civil engineering (General)
Layer (electronics)
lcsh:TK1-9971
Indium
Zdroj: Materials; Volume 11; Issue 1; Pages: 145
Materials, Vol 11, Iss 1, p 145 (2018)
Materials
ISSN: 1996-1944
DOI: 10.3390/ma11010145
Popis: Real time spectroscopic ellipsometry (RTSE) has been applied for in-situ monitoring of the first stage of copper indium-gallium diselenide (CIGS) thin film deposition by the three-stage co-evaporation process used for fabrication of high efficiency thin film photovoltaic (PV) devices. The first stage entails the growth of indium-gallium selenide (In1-xGax)₂Se₃ (IGS) on a substrate of Mo-coated soda lime glass maintained at a temperature of 400 °C. This is a critical stage of CIGS deposition because a large fraction of the final film thickness is deposited, and as a result precise compositional control is desired in order to achieve the optimum performance of the resulting CIGS solar cell. RTSE is sensitive to monolayer level film growth processes and can provide accurate measurements of bulk and surface roughness layer thicknesses. These in turn enable accurate measurements of the bulk layer optical response in the form of the complex dielectric function e = e₁ - ie₂, spectra. Here, RTSE has been used to obtain the (e₁, e₂) spectra at the measurement temperature of 400 °C for IGS thin films of different Ga contents (x) deduced from different ranges of accumulated bulk layer thickness during the deposition process. Applying an analytical expression in common for each of the (e₁, e₂) spectra of these IGS films, oscillator parameters have been obtained in the best fits and these parameters in turn have been fitted with polynomials in x. From the resulting database of polynomial coefficients, the (e₁, e₂) spectra can be generated for any composition of IGS from the single parameter, x. The results have served as an RTSE fingerprint for IGS composition and have provided further structural information beyond simply thicknesses, for example information related to film density and grain size. The deduced IGS structural evolution and the (e₁, e₂) spectra have been interpreted as well in relation to observations from scanning electron microscopy, X-ray diffractometry and energy-dispersive X-ray spectroscopy profiling analyses. Overall the structural, optical and compositional analysis possible by RTSE has assisted in understanding the growth and properties of three stage CIGS absorbers for solar cells and shows future promise for enhancing cell performance through monitoring and control.
Databáze: OpenAIRE
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