Interfaces effectives et pentes d'Urbach de multicouches a-Si:H/a-SiNx:H

1992 ◽  
Vol 70 (10-11) ◽  
pp. 824-829 ◽  
Author(s):  
M. Beaudoin ◽  
M. Meunier ◽  
T. Muschik ◽  
R. Schwarz ◽  
C. J. Arsenault ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Double Layers ◽  
Effective Width ◽  
Constant Composition ◽  
X Ray ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous ◽  
Interface Effects

Optical and structural measurements are presented for glow discharge multilayer structures of hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon nitride (a-SiNx:H). Two sets of samples are presented. For set A, the barrier thickness as well as the number of double layers are kept constant whereas, for set B, samples have both constant composition and total thickness. Small-angle X-ray reflectivity measurements (reflectometry) are analyzed using a theoretical model based on the transfer matrix method. This analysis yields an effective width between 1.5 and 2.0 nm for the interfaces. The increase of the Urbach slope parameter with decreasing well layer thickness is measured by photothermal deflection spectroscopy and by Fourier transform photoacoustic spectroscopy. This dependence is analyzed by taking into account the effective interface thickness and it is studied by using the optical absorption model of Abe and Toyozawa (J. Phys. Soc. Jpn. 50, 2185 (1981)). Both sets of samples show the same behavior, which leads to the conclusion that the Urbach slope increase is due to interface effects.

Defects in Hydrogenated Amorphous Silicon Carbide Alloys using Electron Spin Resonance and Photothermal Deflection Spectroscopy

2009 ◽  
Vol 1153 ◽  
Author(s):  
Brian J. Simonds ◽  
Feng Zhu ◽  
Josh Gallon ◽  
Jian Hu ◽  
Arun Madan ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Electron Spin Resonance ◽  
Amorphous Silicon ◽  
Electron Spin ◽  
Carbon Concentration ◽  
Hydrogenated Amorphous Silicon ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

AbstractHydrogenated amorphous silicon carbide alloys are being investigated as a possible top photoelectrode in photoelectrochemical cells used for hydrogen production through water splitting. In order to be used as such, it is important that the effects of carbon concentration on bonding, and thus on the electronic and optical properties, is well understood. Electron spin resonance experiments were performed under varying experimental conditions to study the defect concentrations. The dominant defects are silicon dangling bonds. At room temperature, the spin densities varied between 1016 and 1018 spins/cm3 depending on the carbon concentration. Photothermal deflection spectroscopy, which is an extremely sensitive measurement of low levels of absorption in thin films, was performed to investigate the slope of the Urbach tail. These slopes are 78 meV for films containing the lowest carbon concentration and 98 meV for those containing the highest carbon concentration.

Hydrogenated Amorphous Silicon Films by the Pyrolysis of Disilane(1)

1985 ◽  
Vol 49 ◽  
Author(s):  
T. L. Chu ◽  
Shirley S. Chu ◽  
S. T. Ang ◽  
D. H. Lo ◽  
A. Duong ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Amorphous Silicon ◽  
Deposition Rate ◽  
Hydrogenated Amorphous Silicon ◽  
Conductivity Ratio ◽  
Helium Flow ◽  
Photothermal Deflection Spectroscopy ◽  
Photothermal Deflection ◽  
Gap States ◽  
Hydrogenated Amorphous

AbstractThe thermal decomposition of disilane in a hydrogen or helium flow has been used for the deposition of hydrogenated amorphous silicon (a-Si:H) films on the surface of several substrates at 450°-500°C. The concentration of disilane in the reaction mixture has been found to affect strongly the deposition rate and the photoconductivity of a-Si:H films. The AMI conductivity of a-Si:H films increases with increasing disilane concentration and approaches lO−5(ohm-cm)−l at disilane concentrations higher than about 4%, and the conductivity ratio is about lO5. The density of gap states in CVD a-Si:H films have been determined by the photothermal deflection spectroscopy, capacitancetemperature, capacitance-frequency, and space-charged-limited current measurements with similar results.

Hydrogenated Amorphous Silicon Alloyed with Selenium

1998 ◽  
Vol 507 ◽  
Author(s):  
Shenlin Chen ◽  
P. C. Taylor ◽  
J. M. Viner
Keyword(s):  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
Band Tail ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photo Conductivity ◽  
Photothermal Deflection ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated amorphous silicon alloyed with selenium has been made by plasma enhanced chemical vapor deposition (PECVD). The activation energy for electrical conduction is essentially unchanged for selenium concentrations < 1 at.%. The photo conductivity changes for selenium concentrations > 0.5 at. %. Photothermal deflection spectroscopy (PDS) and electron spin resonance (ESR), respectively, show that the width of the valence band tail states and the density of neutral silicon dangling bonds also change for selenium concentrations > 0.5 at. %.

Hydrogenated Nanocrystalline Silicon Thin Film Transistor Array for X-ray Detector Application

2008 ◽  
Vol 1066 ◽  
Author(s):  
Kyung-Wook Shin ◽  
Mohammad R. Esmaeili-Rad ◽  
Andrei Sazonov ◽  
Arokia Nathan
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Threshold Voltage ◽  
Hydrogenated Amorphous Silicon ◽  
Nanocrystalline Silicon ◽  
Amorphous Selenium ◽  
Breakdown Field ◽  
Storage Capacitor ◽  
X Ray ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF) of 0.15 cm2/V·s, a threshold voltage (VTh) of 5.71 V, and a subthreshold leakage current (Isub) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.

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