Charge transport through localized states in sputtered amorphous silicon suboxides

2001 ◽  
Vol 666 ◽  
Author(s):  
J.J. van Hapert ◽  
N. Tomozeiu ◽  
E.E. van Faassen ◽  
A.M. Vredenberg ◽  
F.H.P.M. Habraken
Keyword(s):  
Amorphous Silicon ◽  
Defect Density ◽  
Rf Magnetron Sputtering ◽  
Quantitative Information ◽  
Thin Layers ◽  
Localized States ◽  
Variable Range Hopping ◽  
Defect States ◽  
Variable Range ◽  
Spin Resonance

ABSTRACTUsing an RF magnetron sputtering technique, thin layers (∼500 nm) of amorphous silicon suboxides (a-SiOx) were deposited, with oxygen/silicon ratios x ranging from 0 to 1.8. These layers contain a large density (1020−1021 cm−3) of, mostly silicon dangling bond, defect states. The level of conduction decreases several orders of magnitude with increasing x. The temperature dependence of the DC conductivity showed that the variable range hopping conduction mechanism is dominant for all x, over the temperature range 30- 330 K. In this mechanism the extent of localization and density of states around the Fermi level determine the conductance. We conclude that the decrease in conductance with increasing oxygen content must, for a large part, be due to a variation in the localization, since Electron Spin Resonance (ESR) measurements showed no decrease in defect density with increasing x. We performed DC conduction measurements at both low and high electric field strengths, showing phenomena, which are consistently desribed within the variable range hopping (VRH) model. These measurements allow the extraction of quantitative information, concerning both the localization and the density of the states involved in the hopping process.

1/f Noise in Mott Variable Range Hopping Conduction in p-type Amorphous Silicon

2015 ◽  
Vol 1770 ◽  
pp. 25-30 ◽  
Author(s):  
V.C. Lopes ◽  
A.J. Syllaios ◽  
D. Whitfield ◽  
K. Shrestha ◽  
C.L. Littler
Keyword(s):  
Electrical Conductivity ◽  
Amorphous Silicon ◽  
Chemical Vapor ◽  
Variable Range Hopping ◽  
Temperature Dependent ◽  
Noise Component ◽  
Variable Range ◽  
Noise Measurements ◽  
P Type ◽  
Hydrogenated Amorphous

ABSTRACTWe report on electrical conductivity and noise measurements made on p-type hydrogenated amorphous silicon (a-Si:H) thin films prepared by Plasma Enhanced Chemical Vapor Deposition (PECVD). The temperature dependent electrical conductivity can be described by the Mott Variable Range Hopping mechanism. The noise at temperatures lower than ∼ 400K is dominated by a 1/f component which follows the Hooge model and correlates with the Mott conductivity. At high temperatures there is an appreciable G-R noise component.

Processing and Characterization of Amorphous Copper Oxide Thin Films Prepared by Reactive Magnetron Sputtering

2018 ◽  
Vol 775 ◽  
pp. 238-245 ◽  
Author(s):  
Thitinai Gaewdang ◽  
Ngamnit Wongcharoen
Keyword(s):  
Thin Films ◽  
Low Temperature ◽  
Magnetron Sputtering ◽  
Copper Oxide ◽  
Flow Rate ◽  
Localized States ◽  
Positive Sign ◽  
Variable Range Hopping ◽  
Variable Range ◽  
Deposited Films

In this paper, copper oxide (CuOx) thin films with amorphous phase were prepared on glass substrates by reactive dc magnetron sputtering. The influence of the flow rate of O2 on the structural, optical and electrical properties of the as-deposited films was systematically studied. XRD revealed that the as-deposited films remained amorphous in the whole range of adjusted oxygen flow rate. Surface morphology and nanoparticle size of the films were observed by AFM. Electrical resistivity and Hall effect measurements were performed on the films with van der Pauw configuration. The positive sign of the Hall coefficient confirmed the p-type conductivity in all studied films. From temperature-dependent electrical conductivity of the films prepared at R(O2) of 1.5 sccm, it was show that three types of behavior can be expected, nearest-neighbor hopping at high temperature range (200-300 K), the Mott variable range hopping at low temperature (110-190 K) and Efros-Shklovskii variable range hopping at very low temperature (65-100 K). Some important parameters corresponding to Mott-VRH and ES-VRH like density of localized states near the Fermi level, localization length, degree of disorder, hopping distance and hopping energy were determined. These parameters would be helpful for optimizing the performance of photovoltaic applications.

Variable range hopping in hydrogenated amorphous silicon

2004 ◽  
Vol 1 (1) ◽  
pp. 101-104 ◽  
Author(s):  
I. P. Zvyagin ◽  
I. A. Kurova ◽  
N. N. Ormont
Keyword(s):  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Variable Range Hopping ◽  
Variable Range ◽  
Hydrogenated Amorphous

Stability in Amorphous Silicon

1987 ◽  
Vol 95 ◽  
Author(s):  
Z E. Smith ◽  
S. Wagner
Keyword(s):  
Electron Spin Resonance ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Thermal Recovery ◽  
Defect States ◽  
Spin Resonance ◽  
Resonance Data ◽  
Electron Spin Resonance Data ◽  
Gap States ◽  
Hydrogenated Amorphous

AbstractThe experimental phenomena associated with light-induced degradation and thermal recovery of hydrogenated amorphous silicon (a-Si:H) films are reviewed, with special emphasis on the limitations of each experimental technique. When several techniques are used in concert, a fuller picture emerges. Recent experiments suggest different positions in the band-gap of the paramagnetic-associated defect states (the dangling bonds) for doped and undopedfilms; this information can be combined with conductivity, sub-bandgap optical absorption and electron spin resonance data to yield a model for the density of gap states (DOS) in a- Si:H, including how the DOS changes upon illumination and annealing.

Dependence of Steady-State Defect Density in Hydrogenated Amorphous Silicon on Carrier Generation Rate Studied Over a Wide Range

1993 ◽  
Vol 297 ◽  
Author(s):  
Nobuhiro Hata ◽  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Steady State ◽  
Amorphous Silicon ◽  
Defect Density ◽  
Hydrogenated Amorphous Silicon ◽  
Continuous Light ◽  
Effective Rate ◽  
Defect States ◽  
Carrier Generation ◽  
Wide Range ◽  
Hydrogenated Amorphous

Measurements of the steady-state defect density (Nst) in hydrogenated amorphous silicon under illumination of pulse-laser light, as well as of continuous light, were carried out; and the dependence of Nst on the effective rate of carrier generation (G) is presented. The values of G ranged from 8 x 1021 to 2.4 × 1023 cm-3 s-1, while the illumination temperature was kept at 30 °C or at 105 °C. The results showed trends of Nst increasing with G similarly to the trends in the literature, but covered a higher and wider G range, and fitted a defect model which assumes a limited number of possible defect states.

Localized States in Electron-Irradiated GaAs

1991 ◽  
Vol 235 ◽  
Author(s):  
S. D. Kouimtzi ◽  
C. Melidis ◽  
C. Achtlleos
Keyword(s):  
Frequency Dependence ◽  
Electron Irradiation ◽  
Localized States ◽  
Variable Range Hopping ◽  
Defect Band ◽  
Variable Range ◽  
Sufficient Degree ◽  
Degree Of Damage ◽  
Band Tailing

ABSTRACTBand tailing produced by electron irradiation of n-type GaAs at helium temperatures is studied. It has been observed that conductance in the band tailing occurs via localized states as evidenced by the observation of a conductance having a frequency dependence of the form σ⊥ωs where ≈ 1.Sufficient degree of damage induces variable range hopping, σ ∝ exp (-b/Tl/4) in a defect band. The frequency dependence of the conductivity in this band is very weak.

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