A Comparative Study of Defect States in Light-Soaked and High-Temperature-Annealed a-Si:H

1993 ◽  
Vol 297 ◽  
Author(s):  
Z. M. Saleh ◽  
H. Tarui ◽  
S. Tsuda ◽  
S. Nakano ◽  
Y. Kuwano
Keyword(s):  
High Temperature ◽  
Light Exposure ◽  
Dark Conductivity ◽  
Defect States ◽  
Narrow Component ◽  
Spin Resonance ◽  
The Difference ◽  
Increasing Temperature ◽  
Induced Changes ◽  
Induced Defects

Our previous results of light-induced electron spin resonance (LESR) indicate that, in hydrogenated amorphous silicon (a-Si:H), light-induced defects differ from those formed during deposition or high-temperature annealing. A plausible interpretation, in which light-induced defects occupy higher-energy states, was proposed to explain these differences. In this study, the constant photocurrent method (CPM), dark conductivity and steady-state (SS) LESR are used to supply new evidence for the difference and conduct two important tests on our hypothesis. In striking agreement with our predictions, we find that the light-induced changes in the SS-LESR lineshape (a decrease in the narrow component relative to the broad one upon light exposure) become indeed more dramatic as the demarcation energies move closer to the midgap by increasing temperature or decreasing bias-light intensity for SS-LESR.

Evolution of D0 and non-D0 Light Induced Defect States in a-Si:H Materials and Their Respective Contribution to Carrier Recombination

2004 ◽  
Vol 808 ◽  
Author(s):  
J. M. Pearce ◽  
J. Deng ◽  
V. Vlahos ◽  
R. W. Collins ◽  
C. R. Wronski ◽  
...  
Keyword(s):  
Room Temperature ◽  
Defect States ◽  
Carrier Recombination ◽  
Spin Resonance ◽  
Respective Contribution ◽  
Gap States ◽  
Induced Changes ◽  
Induced Defects ◽  
Kinetics Of ◽  
Absorption Measurements

A study has been carried out on the evolution of light induced defects in protocrystalline (diluted) a-Si:H films under 1 sun illumination. A room temperature reversal is observed in the photocurrents at 25°C, which is consistent with the relaxation in the recombination currents on corresponding p-i-n solar cells. It is also consistent with the pressure of “fast” states such as have been observed after high intensity illumination. Even with the limitations imposed by the relaxation in the light induced changes on the subgap absorption measurements, the evolution of distinctly different gap states centered around 0.9 and 1.15eV from the conduction band was identified. The kinetics of the electron occupied states, kN(E), at these two energies is compared with that of the neutral dangling bond (D0) densities as measured with electron spin resonance. Because of the similarity between the preliminary results of these kinetics it has not been possible to identify which states correspond to the D0 nor to draw any reliable conclusions about the nature of the different states.

Evolution of Charged Gap Statesin a- Si:H Under Light Exposure

2003 ◽  
Vol 762 ◽  
Author(s):  
M. Zeman ◽  
V. Nádaždy ◽  
R.A.C.M.M. van Swaaij ◽  
R. Durný ◽  
J.W. Metselaar
Keyword(s):  
Deep Level ◽  
Light Exposure ◽  
Dark Conductivity ◽  
Initial Energy ◽  
Energy Distributions ◽  
Transient Spectroscopy ◽  
Induced Changes ◽  
Hydrogenated Amorphous ◽  
Kinetics Of ◽  
Positively Charged

AbstractThe charge deep-level transient spectroscopy (Q-DLTS) experiments on undoped hydrogenated amorphous silicon (a-Si:H) demonstrate that during light soaking the states in the upper part of the gap disappear, while additional states around and below midgap are created. Since no direct correlation is observed in light-induced changes of the three groups of states that we identify from the Q-DLTS signal, we believe that we deal with three different types of defects. Positively charged states above midgap are related to a complex formed by a hydrogen molecule and a dangling bond. Negatively charged states below midgap are attributed to floating bonds. Various trends in the evolution of dark conductivity due to light soaking indicate that the kinetics of light-induced changes of the three gap-state components depend on their initial energy distributions and on the spectrum and intensity of light during exposure.

Light-Soaking Effects on Photoconductivity in a-Si:H Thin Films

1997 ◽  
Vol 467 ◽  
Author(s):  
E. Morgado ◽  
M. Rebelo da Silva ◽  
R. T. Henriques
Keyword(s):  
Thin Films ◽  
Defect Density ◽  
Light Exposure ◽  
Dangling Bond ◽  
Photothermal Deflection Spectroscopy ◽  
Spin Resonance ◽  
Photo Conductivity ◽  
Photothermal Deflection ◽  
Gap States ◽  
Induced Defects

ABSTRACTMetastable defects have been created by light exposure in thin films of a-Si:H. The samples have been characterized by Photothermal Deflection Spectroscopy, Electron Spin Resonance, dark- and photo-conductivity. The experimental results are consistent with numerical calculations with a recombination model involving band tails and one class of correlated dangling-bond states. The effects of light-soaking on the ligh intensity and defect density dependences of photoconductivity are reproduced by the calculations. The model allows to explain the experimental trends by changes in the electronic occupation of the gap states produced by light-induced defects.

Contributions of D0 and non-D0 Gap States to the Kinetics of Light Induced Degradation of Amorphous Silicon under 1 sun Illumination

2001 ◽  
Vol 664 ◽  
Author(s):  
J. Pearce ◽  
X. Niu ◽  
R. Koval ◽  
G. Ganguly ◽  
D. Carlson ◽  
...  
Keyword(s):  
Amorphous Silicon ◽  
Degradation Kinetics ◽  
Hydrogen Dilution ◽  
Spin Resonance ◽  
The Creation ◽  
Staebler Wronski Effect ◽  
Gap States ◽  
Induced Changes ◽  
Induced Defects ◽  
Hydrogenated Amorphous

ABSTRACTLight induced changes to 1 sun degraded steady state (DSS) have been investigated on hydrogenated amorphous silicon (a-Si:H) p-i-n solar cells and corresponding films fabricated with and without hydrogen dilution of silane. Striking similarities are found for the degradation kinetics, between the electron mobility lifetime (μτ) products and the corresponding fill factors (FF). These correlations that exist for both intrinsic materials at temperatures between 25 and 100°C, are present for the DSS as well as in the kinetics, which exihibit distinctly different dependence on temperature. No such correlations are present between μτ, FF and densities of D0 defects, measured with subgap absorption α(E) at 1.2eV, and electron spin resonance (ESR). The creation of non-D0 defects is also clearly indicated by the temperature dependence of the kinetics and the changes in the shape of α(E) with the results suggesting the presence of more than one mechanism for the creation of light induced defects associated with the Staebler-Wronski effect (SWE).

Atmospheric aging and light-induced degradation of amorphous and nanostructured silicon using photoconductivity and electron spin resonance

2014 ◽  
Vol 92 (7/8) ◽  
pp. 713-717 ◽  
Author(s):  
Z.M. Saleh ◽  
G. Nogay ◽  
E. Ozkol ◽  
G. Yilmaz ◽  
M. Sagban ◽  
...  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Light Exposure ◽  
Chemical Vapor ◽  
Dark Conductivity ◽  
Pure Oxygen ◽  
Microcrystalline Silicon ◽  
Nanostructured Silicon ◽  
Dual Beam ◽  
Spin Resonance

Previous studies indicate that the dark conductivity in amorphous and microcrystalline silicon may increase or decrease with exposure to deionized water (DIW) or pure oxygen at 80 °C but always decreases with light exposure. While the light-induced effect is linked to paramagnetic dangling bonds (Do), the origin of metastability in microcrystalline silicon remains unclear. In this study, we use steady-state photoconductivity (SSPC), dual-beam photoconductivity (DBP), and electron spin resonance (ESR), to study the behaviors under soaking in DIW and (or) pure oxygen at 80 °C and light-exposure of amorphous (a-Si:H) and nanostructured (nc-Si:H) silicon samples deposited in a capacitively coupled plasma-enhanced chemical vapor deposition system. Powders from thick samples of low and high crystallinity (Xc) peeling off large substrates were collected in quartz tubes for ESR measurements. Dark conductivity decreases upon exposure to pure oxygen at 80 °C for nc-Si:H but remains unchanged for a-Si:H. The ESR signal attributed to Do decreases with soaking in DIW for high and low crystallinity nc-Si:H but the effect is more significant for higher Xc. Changes in SSPC, DBP, and ESR are used to compare the degradation mechanisms because of O2 exposure and light for amorphous and nanostructured silicon.

Temperature Dependence of the Photoinduced Degradation and Annealing in a-Si:H

2000 ◽  
Vol 609 ◽  
Author(s):  
Niko Schultz ◽  
P. Craig Taylor
Keyword(s):  
Temperature Dependence ◽  
Room Temperature ◽  
Dangling Bond ◽  
Defect States ◽  
Slow Increase ◽  
Spin Resonance ◽  
The Difference ◽  
Kinetics Of ◽  
Defect Densities ◽  
Spin Densities

ABSTRACTWe investigated the temperature dependence of the production and annealing kinetics of the light induced defect states in a:Si:H by electron spin resonance (ESR). At low temperatures (T ∼ 25 K) the silicon dangling bond production is about half as efficient as it is at 300 K. Defects, which are created below about 100 K, almost entirely anneal at room temperature. A sample of a-Si:H, which is subjected to several photo-excitation and annealing cycles, shows a very slow increase of both the degraded and annealed defect densities. The difference in the spin densities between the annealed and degraded states decreases with an increasing number of degradation/annealing cycles.

Radiation Induced Effects on Properties of Semiconducting Nanomaterials

2015 ◽  
Vol 239 ◽  
pp. 1-36 ◽  
Author(s):  
S.K. Tripathi ◽  
Jagdish Kaur ◽  
R. Ridhi ◽  
Kriti Sharma ◽  
Ramneek Kaur
Keyword(s):  
Heavy Ion ◽  
Irradiation Effect ◽  
Defect States ◽  
Γ Irradiation ◽  
Beneficial Effects ◽  
Radiation Induced ◽  
Induced Changes ◽  
Induced Defects ◽  
The Impact ◽  
Irradiation Induced Defects

The irradiation of nanomaterials with energetic particles has significant effects on the properties of target materials. In addition to the well-known detrimental effects of irradiations, they have also some beneficial effects on the properties of nanomaterials. Irradiation effect can change the morphology of the materials in a controlled manner and tailor their mechanical, structural, optical and electrical properties. Irradiation induced modifications in the properties of nanomaterials can be exploited for many useful applications. With the aim of getting better performance of electronic devices, it is necessary to discuss the irradiation induced changes in the nanomaterials. In order to improve the irradiation hardness of electronic components, it is also crucial to have a fundamental understanding of the impact of the irradiation on the defect states and transport properties of the host material. In the present article, we review some recent advances on the irradiation induced effects on the properties of semiconducting nanomaterials. We have reviewed the effect of different types of irradiations which includes γ-irradiation, electron beam irradiation, laser irradiation, swift heavy ion irradiations, thermal induced, and optical induced irradiations, etc. on the various properties of semiconducting nanomaterials. In addition, the irradiation induced defects are also discussed.

Persistent Photoconductivity, the Staebler-Wronski Effect, and Long-Range Disorder in a-Si:H

1997 ◽  
Vol 467 ◽  
Author(s):  
D. Quicker ◽  
P. W. West ◽  
J. Kakalios
Keyword(s):  
Long Range ◽  
Light Exposure ◽  
Activation Energies ◽  
Statistical Properties ◽  
Persistent Photoconductivity ◽  
Conductance Fluctuations ◽  
Before And After ◽  
The Difference ◽  
Staebler Wronski Effect ◽  
Induced Changes

ABSTRACTWe report measurements of the conductivity, thermopower, and conductance fluctuations before and after light exposure for a-Si:H samples that show either persistent photoconductivity (PPC) or a Staebler-Wronski effect. Both the conductivity and thermopower are changed by light exposure, but no change is observed in the difference between the conductivity and thermopower activation energies for any of the samples studied here. This suggests that the long-range disorder is unaffected by light exposure. For some samples, the magnitude or statistical properties of the conductance fluctuations are affected by light exposure. We compare these results to previous studies of the Staebler-Wronski effect and discuss their implications for models of the light-induced changes and the 1/f noise in a-Si:H.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

Light-induced changes in dark conductivity of Kapton

1984 ◽  
Author(s):  
M. LEUNG ◽  
M. TUELING ◽  
P. MIZERA
Keyword(s):  
Dark Conductivity ◽  
Induced Changes
Sign in / Sign up

Export Citation Format

Share Document