Real-Time Spectroscopic Ellipsometry of Sputtered CdTe Thin Films: Effect of Ar Pressure on Structural Evolution and Photovoltaic Performance

2009 ◽  
Vol 1165 ◽  
Author(s):  
Michelle Nicole Sestak ◽  
Jian Li ◽  
Naba Raj Paudel ◽  
Kristopher Wieland ◽  
Jie Chen ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Volume Fraction ◽  
Photovoltaic Performance ◽  
Structural Evolution ◽  
Ex Situ ◽  
Force Microscopy ◽  
Bulk Layer ◽  
Cdte Films

AbstractIn this study, 1 μm thick polycrystalline CdTe films were deposited by magnetron sputtering using a variable argon pressure, 2.5 ≤ pAr ≤ 50 mTorr, and a fixed substrate temperature, Ts = 230°C. Real time spectroscopic ellipsometry (RTSE) was performed during deposition in order to analyze the nucleation and coalescence, as well as the evolution of the surface roughness thickness ds with bulk layer thickness db and the depth profile in the void volume fraction fv. A linear correlation was found between the final ds value measured by RTSE at the end of deposition and the root-mean-square (rms) surface roughness measured by atomic force microscopy (AFM) ex situ after deposition. A monotonic decrease in RTSE-determined roughness thickness is observed with decreasing Ar pressure from 18 to 2.5 mTorr. The lowest pressure also leads to the greatest bulk layer structural uniformity; in this case, fv increases to 0.04 with increasing CdTe thickness to 1 μm. The photovoltaic performance of CdTe films prepared with the lowest pressure of pAr = 2.5 mTorr is compared with that of previously optimized CdTe solar cells with pAr = 10 mTorr.

Mapping the Phase-Change Parameter Space of Hot-Wire CVD Si:H Films Using In-Situ Real Time Spectroscopic Ellipsometry

2002 ◽  
Vol 715 ◽  
Author(s):  
Dean H. Levi ◽  
Brent P. Nelson ◽  
John D. Perkins
Keyword(s):  
Surface Roughness ◽  
Real Time ◽  
Parameter Space ◽  
Spectroscopic Ellipsometry ◽  
Film Growth ◽  
Growth Parameter ◽  
Ex Situ ◽  
Degree Of Crystallinity ◽  
Hot Wire

AbstractIn-situ real-time spectroscopic ellipsometry (RTSE) provides detailed information on the evolution of the structural and optical properties of Si:H films during film growth. We have used in-situ RTSE to characterize the film morphology and crystallinity of hot-wire CVD (HWCVD) Si:H films as a function of hydrogen dilution R=[H]/[H+SiH4], substrate temperature Ts, and film thickness db. Transitions from one mode of film growth to another are indicated by abrupt changes in the magnitude of the surface roughness during film growth. The degree of crystallinity of the film can be determined from the bulk dielectric function. We have studied the growth parameter space consisting of R from 0 to 12, Ts from 150°C to 550°C, and db from 0 to 1 um. For each set of R and Ts values, the structural evolution of the film can be characterized by the shape of the surface roughness thickness ds versus bulk thickness db curve. In contrast to studies done by Collins et al on PECVD growth of Si:H films, our studies of HWCVD growth find no conditions where ds remains constant after coalescence of the initial nucleation centers. Most of the films grown within the range of parameters studied exhibit a secondary nucleation and coalescence signature. The transition between a-Si:H and uc-Si:H growth is near the R=3 to R=4 dividing line. Initial coalescence of purely uc-Si:H material doesn't occur until R>8. We have verified the RTsE crystallinity classification using ex-situ Raman scattering.

Real Time Monitoring of Amorphous Silicon Solar Cell Fabrication

1995 ◽  
Vol 377 ◽  
Author(s):  
Yiwei Lu ◽  
Sangbo Kim ◽  
J. S. Burnham ◽  
Ing-Shin Chen ◽  
Yeeheng Lee ◽  
...  
Keyword(s):  
Solar Cell ◽  
Real Time ◽  
Volume Fraction ◽  
Structural Parameters ◽  
Type A ◽  
Force Microscopy ◽  
Bulk Layer ◽  
Amorphous Silicon Solar Cell ◽  
The Individual ◽  
P Type

ABSTRACTWe have applied real time spectroscopie ellipsometry (RTSE) to monitor the successive growth of p-type a-Si1-xCx:H and i-type a-Si:H on specular SnO2:F (i.e., the superstrate solar cell configuration) in a single-chamber deposition system. Both the microstructural evolution, which includes the surface roughness and bulk layer thicknesses versus time and bulk layer void volume fraction, as well as the optical properties, which include the dielectric function (1.5–4.0 eV) and optical gap of the individual layers, were determined from RTSE data collected during growth. The accuracy of our approach is demonstrated by correlating structural parameters obtained both by RTSE and atomic force microscopy. Based on prior information deduced by RTSE, the TCO/p/i structure was fabricated with optimized procedures that have sought to minimize TCO/'p and p/i interfacial problems. These studies illustrate that RTSE can be a valuable tool for identifying problems in the fabrication of a-Si:H solar cells and ultimately improving cell performance.

Evolution of Crystallinity in Mixed-Phase (a+μc)-Si:H as Determined by Real Time Spectroscopic Ellipsometry

2003 ◽  
Vol 762 ◽  
Author(s):  
A. S. Ferlauto ◽  
G. M. Ferreira ◽  
R.J. Koval ◽  
J.M. Pearce ◽  
C.R. Wronski ◽  
...  
Keyword(s):  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Vapor Deposition ◽  
Volume Fraction ◽  
Cone Angle ◽  
Chemical Vapor ◽  
Mixed Phase ◽  
Thin Film Solar Cells ◽  
Nucleation Density ◽  
Microcrystalline Silicon

AbstractThe ability to characterize the phase of the intrinsic (i) layers incorporated into amorphous silicon [a-Si:H] and microcrystalline silicon [μc-Si:H] thin film solar cells is critically important for cell optimization. In our research, a new method has been developed to extract the thickness evolution of the μc-Si:H volume fraction in mixed phase amorphous + microcrystalline silicon [(a+μc)-Si:H] i-layers. This method is based on real time spectroscopic ellipsometry measurements performed during plasma-enhanced chemical vapor deposition of the films. In the analysis, the thickness at which crystallites first nucleate from the a-Si:H phase can be estimated, as well as the nucleation density and microcrystallite cone angle. The results correlate well with structural and solar cell measurements.

scholarly journals Surface roughness estimation of MBE grown CdTe/GaAs(211)B by ex-situ spectroscopic ellipsometry

AIP Advances ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 075111 ◽  
Author(s):  
Merve Karakaya ◽  
Elif Bilgilisoy ◽  
Ozan Arı ◽  
Yusuf Selamet
Keyword(s):  
Surface Roughness ◽  
Spectroscopic Ellipsometry ◽  
Ex Situ ◽  
Surface Roughness Estimation

Real Time Spectroscopic Ellipsometry Studies of the Solid Phase Crystallization of Amorphous Silicon

1998 ◽  
Vol 507 ◽  
Author(s):  
H. Fujiwara ◽  
Joohyun Koh ◽  
Yeeheng Lee ◽  
C. R. Wronski ◽  
R. W. Collins
Keyword(s):  
Amorphous Silicon ◽  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Volume Fraction ◽  
Solid Phase ◽  
Thin Layers ◽  
Crystallization Time ◽  
Calibration Data ◽  
Solid Phase Crystallization ◽  
Near Surface

ABSTRACTWe have introduced real time spectroscopic ellipsometry (RTSE) for characterization of the solid phase crystallization (SPC) of intrinsic and n-type amorphous silicon (a-Si:H) thin films. RTSE has several advantages in the study and design of SPC processes for thin film transistor and solar cell fabrication. These include the capability of obtaining (i) calibration data that yield the near surface temperature of the film during processing, (ii) the volume fraction of the crystalline Si component of the film continuously versus time during SPC, and (iii) a measurement of the grain size and quality of the final polycrystalline Si film. For the thin layers studied here (∼150-1000 Å), we demonstrate excellent fitting of the SPC dynamics to the Avrami-Johnson-Mehl theory for random nucleation and two-dimensional crystallite growth. For a-Si:H n-layers, the crystallization time over the range from 565 to 645°C appears to be weakly activated with an energy of 0.6 eV.

Optical and Physical Characterization of Cu2-xSe Thin Films for Real Time Spectroscopic Ellipsometry on Cu(In,Ga)Se2-based Photovoltaic Devices

2009 ◽  
Vol 1210 ◽  
Author(s):  
James D Walker ◽  
Himal Khatri ◽  
Scott Little ◽  
Vikash Ranjan ◽  
Robert Collins ◽  
...  
Keyword(s):  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Growth Temperature ◽  
Room Temperature ◽  
Optical Model ◽  
High Efficiency ◽  
Optical Feedback ◽  
High Surface ◽  
Ex Situ ◽  
Photovoltaic Devices

AbstractIn situ, real time spectroscopic ellipsometry (RTSE) has been used to study the growth processes and optical properties of Cu2-xSe - an important binary compound in the fabrication of high efficiency copper indium gallium diselenide (CIGS) photovoltaic devices. It was found that the high surface roughness of the Cu2-xSe layers necessitated a “graded” optical model in order to extract meaningful dielectric functions at both 550 °C and room temperature. The optical model was verified at room temperature against SEM micrographs and reflectance measurements carried out ex situ. The growth temperature dielectric functions presented in this study are expected to allow for a greater level of control and understanding of the so-called 2- and 3-stage processes for CIGS fabrication in which a Cu2-xSe phase, present at the CIGS grain boundaries, acts as a fluxing agent for the growth of photovoltaic quality CIGS. Real time optical feedback via RTSE combined with the growth temperature dielectric functions presented here could play an important role in improving material fabrication on both the laboratory and industrial scales.

scholarly journals Real time and ex situ spectroscopic ellipsometry analysis microcrystalline silicon thin films growth

2012 ◽  
Vol 61 (3) ◽  
pp. 036802
Author(s):  
Li Xin-Li ◽  
Gu Jin-Hua ◽  
Gao Hai-Bo ◽  
Chen Yong-Sheng ◽  
Gao Xiao-Yong ◽  
...  
Keyword(s):  
Thin Films ◽  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Ex Situ ◽  
Microcrystalline Silicon ◽  
Silicon Thin Films

Roughness evolution of high-rate deposited a-SiNx:H films studied by atomic force microscopy and real time spectroscopic ellipsometry

2004 ◽  
Vol 808 ◽  
Author(s):  
P.J. van den Oever ◽  
M.C.M. van de Sanden ◽  
W.M.M. Kessels
Keyword(s):  
Atomic Force Microscopy ◽  
Silicon Nitride ◽  
Real Time ◽  
Spectroscopic Ellipsometry ◽  
Mass Density ◽  
High Rate ◽  
Growth Exponent ◽  
Force Microscopy ◽  
Atomic Force ◽  
Roughness Exponent

ABSTRACTThe scaling behavior of the roughness evolution of silicon nitride (a-SiNx:H) films with different mass densities (deposited from SiH4-N2-H2 and SiH4-NH3 based plasmas) has been investigated by atomic force microscopy and real time spectroscopic ellipsometry. The observed roughness exponent a is similar for both films, whereas the growth exponent b is a factor of two smaller for the higher density films. The relation between the lower value of b and the higher mass density is discussed.

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