Real-Time ESR Observation During Film Growth of a-Si:H

1997 ◽  
Vol 467 ◽  
Author(s):  
S. Yamasaki ◽  
T. Umeda ◽  
J. Isoya ◽  
K. Tanaka
Keyword(s):  
Gas Phase ◽  
Film Growth ◽  
Hydrogen Plasma ◽  
Bulk Region ◽  
Dangling Bond ◽  
Dynamic Changes ◽  
Spin Resonance ◽  
Higher Spin ◽  
Hydrogenated Amorphous

ABSTRACTIn-situ electron-spin-resonance (ESR) measurements of film growth of hydrogenated amorphous silicon (a-Si:H) using a remote hydrogen plasma technique have been performed. The Si dangling-bond signal in a-Si:H during and after deposition has been detected, in addition to the gas-phase ESR signals both of atomic hydrogen and photo-excited SiHx molecules. Dynamic changes of the Si dangling-bond signal intensity were observed when the deposition started and stopped, which has suggested the existence of a subsurface region with higher spin density than that in the bulk region.

Probing the Elementary Surface Reactions of Hydrogenated Silicon PECVD by In-situ ESR

1998 ◽  
Vol 536 ◽  
Author(s):  
Satoshi Yamasaki ◽  
Claus Malten ◽  
Takehide Umeda ◽  
Jun-Ichi Isoya ◽  
Kazunobu Tanaka
Keyword(s):  
Gas Phase ◽  
Dynamic Change ◽  
Surface Region ◽  
Dangling Bond ◽  
Hydrogenated Silicon ◽  
Plasma Treatments ◽  
Elementary Surface ◽  
Ar Plasma ◽  
Hydrogenated Amorphous

AbstractThe dynamic change of the dangling bond (db) intensity in hydrogenated amorphous silicon (a-Si:H) during H2 and Ar plasma treatments was observed using an in-situ electron-spinresonance (ESR) technique. The experimental results show that the time to reach the steady state between gas-phase H atoms and the a-Si:H surface is less than 1 sec, and Ar plasma treatments create a top-surface region with an extremely high db density.

Control of Materials and Interfaces in μc-Si:H-based Solar Cells Grown at High Rate

2011 ◽  
Vol 1321 ◽  
Author(s):  
Yasushi Sobajima ◽  
Chitose Sada ◽  
Akihisa Matsuda ◽  
Hiroaki Okamoto
Keyword(s):  
Growth Rate ◽  
Solar Cells ◽  
Film Growth ◽  
Defect Density ◽  
Density Measurement ◽  
High Growth ◽  
High Growth Rate ◽  
High Rate ◽  
Bulk Region ◽  
Dangling Bond

ABSTRACTGrowth process of microcrystalline silicon (μc-Si:H) using plasma-enhanced chemicalvapor- deposition method under high-rate-growth condition has been studied for the control of optoelectronic properties in the resulting materials. We have found two important things for the spatial-defect distribution in the resulting μc-Si:H through a precise dangling-bond-density measurement, e. g., (1) dangling-bond defects are uniformly distributed in the bulk region of μc- Si:H films independent of their crystallite size and (2) large number of dangling bonds are located at the surface of μc-Si:H especially when the film is deposited at high growth rate. Starting procedure of film growth has been investigated as an important process to control the dangling-bond-defect density in the bulk region of resulting μc-Si:H through the change in the electron temperature by the presence of particulates produced at the starting period of the plasma. Deposition of Si-compress thin layer on μc-Si:H grown at high rate followed by thermal annealing has been proposed as an effective method to reduce the defect density at the surface of resulting μc-Si:H. Utilizing the starting-procedure-controlling method and the compress-layerdeposition method together with several interface-controlling methods, we have demonstrated the fabrication of high conversion-efficiency (9.27%) substrate-type (n-i-p) μc-Si:H solar cells whose intrinsic μc-Si:H layer is deposited at high growth rate of 2.3 nm/sec.

Surface Processes during Growth of Hydrogenated Amorphous Silicon

2004 ◽  
Vol 808 ◽  
Author(s):  
Eray S. Aydil ◽  
Sumit Agarwal ◽  
Mayur Valipa ◽  
Saravanapriyan Sriraman ◽  
Dimitrios Maroudas
Keyword(s):  
Amorphous Silicon ◽  
Film Growth ◽  
Silicon Film ◽  
Hydrogenated Amorphous Silicon ◽  
Surface Processes ◽  
Atomistic Simulations ◽  
Elementary Surface ◽  
Hydrogenated Amorphous ◽  
And Diffusion

ABSTRACTHydrogenated amorphous silicon films for photovoltaics and thin film transistors are deposited from silane containing discharges. The radicals generated in the plasma such as SiH3 and H impinge on the surface and lead to silicon film growth through a complex network of elementary surface processes that include adsorption, abstraction, insertion and diffusion of various radicals. Mechanism and kinetics of these reactions determine the film composition and quality. Developing deposition strategies for improving the film quality requires a fundamental understanding of the radical-surface interaction mechanisms. We have been using in situ multiple total internal reflection Fourier transform infrared spectroscopy and in situ spectroscopic ellipsometry in conjunction with atomistic simulations to determine the elementary surface reaction and diffusion mechanisms. Synergistic use of experiments and atomistic simulations elucidate elementary processes occurring on the surface. Herein, we review our current understanding of the reaction mechanisms that lead to a-Si:H film growth with special emphasis on the reactions of the SiH3 radical.

Explanation of the Anomalously Large Defect-Optical-Absorption Energies in Doped Amorphous Silicon

1989 ◽  
Vol 149 ◽  
Author(s):  
Howard M. Branz
Keyword(s):  
Optical Absorption ◽  
Amorphous Silicon ◽  
Transition Energy ◽  
Correlation Energy ◽  
Dangling Bond ◽  
Large Defect ◽  
Potential Fluctuations ◽  
Spin Resonance ◽  
P Type ◽  
Hydrogenated Amorphous

ABSTRACTThe longstanding controversy over the anomalously large subgap optical absorption energies in n-type (1.1 eV) and p-type (1.3 eV) hydrogenated amorphous silicon (a-Si:H) is described and resolved. Adler suggested that these large values are incompatible with a positive effective correlation energy of the dangling bond defect and a 1.7 eV bandgap. Kocka proposed that dopant-defect pairing deepens each dangling bond transition energy by about 0.5 eV in doped a-Si:H. I assume no deepening due to pairing, a positive correlation energy of 0.2 eV consistent with the observation of dark electron spin resonance in undoped a-Si:H, and dangling-bond relaxation energies of 0.2 to 0.3 eV which are indicated by previous theoretical and experimental work. The postulate of vertical optical transitions then reduces the anomaly from about 0.9 eV to 0.4 eV. This residual anomaly may be explained by electronic-level deepening in doped a-Si:H caused by disorder-induced potential fluctuations of 0.2 eV half-width.

Hydrogen Collision Model of The Staebler-Wronski Effect: Microscopics and Kinetics

1998 ◽  
Vol 507 ◽  
Author(s):  
Howard M. Branz
Keyword(s):  
Room Temperature ◽  
Pair Creation ◽  
Hole Pair ◽  
Dangling Bond ◽  
Electron Hole ◽  
Spin Resonance ◽  
Electron Hole Pair ◽  
Staebler Wronski Effect ◽  
Hydrogenated Amorphous ◽  
Creation Rate

ABSTRACTA new microscopic and kinetic model of light-induced metastability in hydrogenated amorphous silicon (a-Si:H) is described. Recombination and trapping of photoinduced carriers excite hydrogen from deep Si-H bonds into a mobile configuration, leaving a dangling bond (DB) defect at the site of excitation. Normally, mobile H are recaptured at DB defects and no metastability or net DB production results. However, when two mobile H collide, they form a metastable two-hydrogen complex and leave two spatially-uncorrelated Staebler-Wronski DBs. Thermal and light-induced annealing occur when mobile H are excited from the metastable two-H complex; they diffuse and are recaptured to DBs. The microscopic model is entirely compatible with electron-spin-resonance results showing neither DB-DB nor DB-H spatial correlation of the light-induced DBs. The model leads to new differential equations describing the evolution of the mobile H and DB densities. These equation equations explain the observed room-temperature Ndb∼G2/3t1/3 dependence of DB creation upon the electron-hole pair creation rate (G) and time. The model also accounts for both t1/3-kinetics at 4.2K and t1/2-kinetics under laser-pulse soaking. Neither of these results can be explained within the prevailing electron-hole pair recombination model.

Kinetics of Gas-Phase Chemical Reactions and Growth of a-SiC:H Films from Silane and Acetylene in a Remote Hydrogen Plasma Reactor

1991 ◽  
Vol 219 ◽  
Author(s):  
N. M. Johnson ◽  
Paulo V. Santos ◽  
J. Walker ◽  
K. S. Stevens
Keyword(s):  
Silicon Carbide ◽  
Electron Spin Resonance ◽  
Gas Phase ◽  
Chemical Reactions ◽  
Electron Spin ◽  
Plasma Reactor ◽  
Hydrogen Plasma ◽  
Spin Resonance ◽  
Kinetics Of ◽  
Phase Chemical

ABSTRACTGas-phase chemical reactions of interest for the deposition of amorphous silicon carbide in a remote hydrogen plasma reactor have been quantitatively characterized with electron spin resonance, and the deposition of a-SiC:H from silane and acetylene is demonstrated.

Properties and Local Structure of Plasma-Deposited Amorphous Silicon-Carbon Alloys

1986 ◽  
Vol 70 ◽  
Author(s):  
W. C. Mohr ◽  
C. C. Tsai ◽  
R. A. Street
Keyword(s):  
Substrate Temperature ◽  
Amorphous Silicon ◽  
Gas Phase ◽  
Vacuum Annealing ◽  
Dangling Bond ◽  
Bond Density ◽  
Silicon Carbon ◽  
Back Bonding ◽  
Hydrogenated Amorphous ◽  
Gas Ratio

ABSTRACTHydrogenated amorphous silicon-carbon alloy films were plasma-deposited from metnane and silane, varying gas ratio, R.F. power and substrate temperature. Carbon addition increases the optical gap, but also raises the dangling bond density while decreasing conductivity. Low C alloys can be gas-phase doped both p and n type. In the IR spectra the various Si-C stretching modes observed between 650 and 780 cm-1 are explained by back bonding variations. A tentative method of assigning this shift to back bonding of C to the Si is given. A distribution of modes is observed for all alloys, with each mode appearing even at 2% C. The distribution is sensitive to substrate temperature, but is stable after vacuum annealing to 400°C.

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