Electronic Transitions in Mixed Phase Crystalline/Amorphous Silicon in the Low Crystalline Fraction Regime

1999 ◽  
Vol 557 ◽  
Author(s):  
J. David Cohen ◽  
Daewon Kwon ◽  
Chih-Chiang Chen ◽  
Hyun-Chul Jin ◽  
Eric Hollar ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Cross Section ◽  
Optical Transition ◽  
Electronic Transitions ◽  
Crystalline Fraction ◽  
Silicon Matrix ◽  
Transient Photocurrent ◽  
Dc Reactive Magnetron Sputtering ◽  
Optical Cross Section ◽  
Low Crystalline

AbstractAmorphous silicon films were prepared by dc reactive magnetron sputtering under conditions approaching the phase transition to microcrystallinity. Using TEM imaging these films were found to contain clusters of 5 to 50 nm sized Si crystallites embedded in an amorphous silicon matrix. Photocapacitance and transient photocurrent sub-band-gap optical spectra of this material appear to consist of a superposition of a spectrum typical of amorphous silicon together with an optical transition, with a threshold near 1. 1eV, that exhibits a very large optical cross section. This transition arises from valence band electrons being optically inserted into empty levels lying within the amorphous silicon mobility gap. Using modulated photocurrent methods we have determined that these states also dominate the electron deep trapping in this material. We argue that these states arise from defects at the crystalline-amorphous boundary.

Transient Photocurrent Spectroscopy of Trap Levels in Ultra-Thin SiO2 Films

1996 ◽  
Vol 428 ◽  
Author(s):  
Y. Miura ◽  
S. Fujieda
Keyword(s):  
Cross Section ◽  
Monochromatic Light ◽  
Electron Trap ◽  
External Circuit ◽  
Broad Distribution ◽  
Transient Photocurrent ◽  
Photocurrent Spectroscopy ◽  
Optical Cross Section ◽  
Tunneling Injection ◽  
Trap Levels

AbstractStress-induced trap levels near Si/SiO2 interfaces for MOS diodes with 10 imi-thick oxides are investigated by measuring the transient photocurrent, which depends on the incident photon energy. The electron trap levels are filled by tunneling injection, and the electrons are depopulated by monochromatic light irradiation. The transient photocurrent, which is measured as an external circuit current, decays exponentially with time. Based on a proposed detrapping model, the optical cross section is estimated to be about 1×10−17 cm2 for hv=2−3 eV. The obtained photo-accessible trap density has a broad distribution at around hv=2.5 eV.

Comparison of the Optical Cross Section for the Si Dangling Bond in a- Si:H and At the c - Si/SiO2 Interface

1985 ◽  
Vol 46 ◽  
Author(s):  
W. B. Jackson ◽  
N. M. Johnson
Keyword(s):  
Optical Properties ◽  
Matrix Element ◽  
Amorphous Silicon ◽  
Cross Section ◽  
Hydrogenated Amorphous Silicon ◽  
Optical Measurements ◽  
Dipole Matrix Element ◽  
Dangling Bond ◽  
Optical Cross Section ◽  
Hydrogenated Amorphous

AbstractThe optical properties of the trivalent silicon dangling bond defect in hydrogenated amorphous silicon and at the Si/SiO2 interface are compared. While both defects give rise to ambipolar deep levels within the gap, significant differences in the optical properties between the two systems are found. The absorption in a-Si:H is significantly stronger and is dominated by a transition from the defect to the conduction band while the absorption at the interface is dominated by hole emission. The average dipole matrix element squared is roughly independent of energy in both systems with a magnitude of ∼30Å2. Implications of these results for optical measurements in other silicon systems are discussed.

Deposition and Crystallisation Behaviour of Amorphous Silicon Thin Films Obtained by Pyrolysis of Disilane Gas at Very Low Pressure

1994 ◽  
Vol 345 ◽  
Author(s):  
T. Kretz ◽  
D. Pribat ◽  
P. Legagneux ◽  
F. Plais ◽  
O. Huet ◽  
...  
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Amorphous Silicon ◽  
Vapor Deposition ◽  
Electrical Conductance ◽  
Chemical Vapor ◽  
Crystalline Fraction ◽  
Silicon Thin Films ◽  
Crystallisation Behaviour

AbstractHigh purity amorphous silicon layers were obtained by ultrahigh vacuum (millitorr range) chemical vapor deposition (UHVCVD) from disilane gas. The crystalline fraction of the films was monitored by in situ electrical conductance measurements performed during isothermal annealings. The experimental conductance curves were fitted with an analytical expression, from which the characteristic crystallisation time, tc, was extracted. Using the activation energy for the growth rate extracted from our previous work, we were able to determine the activation energy for the nucleation rate for the analysed-films. For the films including small crystallites we have obtained En ∼ 2.8 eV, compared to En ∼ 3.7 eV for the completely amorphous ones.

Dependence of the optical cross section of interface states on the photon energy at Si-SiO2 structures

1986 ◽  
Vol 168 (1-3) ◽  
pp. 665-671 ◽  
Author(s):  
A. Herms ◽  
J.R. Morante ◽  
J. Samitier ◽  
A. Cornet ◽  
P. Cartujo ◽  
...  
Keyword(s):  
Cross Section ◽  
Photon Energy ◽  
Interface States ◽  
Optical Cross Section

The Defect Structure of BaTiO3 Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
L.A. Wills ◽  
B.W. Wessels
Keyword(s):  
Thin Films ◽  
Cross Section ◽  
Defect Structure ◽  
Oxygen Vacancies ◽  
Vacuum Annealing ◽  
Deep Level ◽  
Energy Levels ◽  
The Other ◽  
Optical Cross Section ◽  
Impurity Defects

AbstractThe defect structure of BaTiO3 thin films grown on (100) Si was examined using transient photocapacitance spectroscopy. The concentration, optical cross section and associated energy levels of both native and impurity defects in as-grown and annealed BaTiO3 films were evaluated. Deep level defects withpeak energies of Ev+1.8, Ev+2.4, Ev+2.7, Ev+3.0-3.1 and Ev+3.2-3.3 eV were observed in the as-grown films. Upon vacuum annealing, the concentration of the traps at Ev+3.0 and Ev+3.2 eV increased while the concentration of the traps at Ev+ 1.8 and Ev+2.4 eV decreased. The levels at Ev+3.0-3.1 and Ev+3.2-3.3 eV are attributed to oxygen vacancies. The other levels are tentatively ascribed to Fe and Fe related defects.

Infrared Electroabsorption Spectra in Amorphous Silicon Solar Cells

1999 ◽  
Vol 557 ◽  
Author(s):  
J. H. Lyou ◽  
Eric A. Schiff ◽  
Steven S. Hegedus ◽  
S. Guha ◽  
J. Yang
Keyword(s):  
Solar Cells ◽  
Infrared Spectrum ◽  
Amorphous Silicon ◽  
Optical Transition ◽  
Silicon Solar Cells ◽  
Reverse Bias Voltage ◽  
Dangling Bond ◽  
Applied Bias ◽  
Infrared Band ◽  
Peak Energy

AbstractWe report measurements of the infrared spectrum detected by modulating the reverse-bias voltage across amorphous silicon pin solar cells and Schottky barrier diodes. We find a band with a peak energy of 0.8 eV. The existence of this band has not, to our knowledge, been reported previously. The strength of the infrared band depends linearly upon applied bias, as opposed to the quadratic dependence for interband electroabsorption in amorphous silicon.The band's peak energy agrees fairly well with the known optical transition energies for dangling bond defects, but the linear dependence on bias and the magnitude of the signal are surprising if interpreted using an analogy to interband electroabsorption. A model based on absorption by defects near the n/i interface of the diodes accounts well for the infrared spectrum.

Optimization of the metal/silicon ratio on nickel assisted crystallization of amorphous silicon

2005 ◽  
Vol 869 ◽  
Author(s):  
L. Pereira ◽  
M. Beckers ◽  
R.M.S. Martins ◽  
E. Fortunato ◽  
R. Martins
Keyword(s):  
Amorphous Silicon ◽  
Spectroscopic Ellipsometry ◽  
Crystallization Time ◽  
Crystalline Fraction ◽  
Nickel Metal ◽  
Metal Induced Crystallization ◽  
Structural Improvement ◽  
Short Annealing ◽  
The One ◽  
Induced Crystallization

AbstractThe aim of this work is to optimize the metal/silicon ratio on nickel metal induced crystallization of silicon. For this purpose amorphous silicon layers with 80, 125 and 220 nm thick were used on the top of which 0.5 nm of Ni was deposited and annealed during the required time to full crystallize the a-Si. The data show that the 80 nm a-Si layer reaches a crystalline fraction of 95.7% (as detected by spectroscopic ellipsometry) after annealed for only 2 hours. No significant structural improvement is detected by ellipsometry neither by XRD when annealing the films for longer times. However, on 125 nm thick samples, after annealing for 2 hours the crystalline fraction is only 59.7%, reaching a similar value to the one with 80 nm only after 5 hours, with a crystalline fraction of 92.2%. Here again no significant improvements were achieved by using longer annealing times. Finally, the 220 nm thick a-Si sample is completely crystallized only after 10 hours annealing. These data clear suggest that the crystallization of thicker a-Si layers requires thicker Ni films to be effective for short annealing times. A direct dependence of the crystallization time on the metal/silicon ratio was observed and estimated.

Sign in / Sign up

Export Citation Format

Share Document