Optical and electronic properties of amorphous SiNx:H alloy films

1985 ◽  
Vol 63 (6) ◽  
pp. 846-851 ◽  
Author(s):  
T. V. Herak ◽  
R. D. McLeod ◽  
M. G. Collett ◽  
K. C. Kao ◽  
H. C. Card ◽  
...  
Keyword(s):  
Nitrogen Content ◽  
Electronic Properties ◽  
Optical Excitation ◽  
Dark Conductivity ◽  
Dangling Bond ◽  
Alloy Films ◽  
Optical And Electronic Properties ◽  
Rf Glow Discharge ◽  
Gap States ◽  
Induced Changes

The optical and electronic properties of a-SiNx:H alloy films fabricated by rf glow discharge have been measured for 0 ≤ x ≤ 0.6. The material is dispersive over the range of photon energies 0.5 ≤ hv ≤ 3.5 eV. The optical gap is about 1.65 eV and is practically independent of x for 0.1 < x < 0.4, but it increases rapidly with increasing x for 0 < x < 0.1 and x > 0.4. For x > 0.6 the refractive index approaches the value for Si3N4. The dark conductivity, the photoconductivity, and the ratio of the photoconductivity to the dark conductivity are enhanced by nitrogen incorporation when appropriate nitrogen content is used. All the experimental results indicate that the incorporated nitrogen does not act as a dopant, but rather acts as a dangling-bond compensator. Photo-induced changes in both dark conductivity and photoconductivity due to high-intensity optical excitation have been observed. The degree of such changes decreases with increasing nitrogen content. This phenomenon is attributed to the photo-induced change in the microstructure of the films that leads to a change in both the density and the distribution of gap states.

scholarly journals Defect Processes in Halogen Doped SnO2

2021 ◽  
Vol 11 (2) ◽  
pp. 551
Author(s):  
Petros-Panagis Filippatos ◽  
Nikolaos Kelaidis ◽  
Maria Vasilopoulou ◽  
Dimitris Davazoglou ◽  
Alexander Chroneos
Keyword(s):  
Electronic Properties ◽  
Tin Oxide ◽  
Density Functional ◽  
Structural Changes ◽  
High Dielectric Constant ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Optical And Electronic Properties ◽  
High Dielectric ◽  
Gap States

In the present study, we performed density functional theory calculations (DFT) to investigate structural changes and their impact on the electronic properties in halogen (F, Cl, Br, and I) doped tin oxide (SnO2). We performed calculations for atoms intercalated either at interstitial or substitutional positions and then calculated the electronic structure and the optical properties of the doped SnO2. In all cases, a reduction in the bandgap value was evident, while gap states were also formed. Furthermore, when we insert these dopants in interstitial and substitutional positions, they all constitute a single acceptor and donor, respectively. This can also be seen in the density of states through the formation of gap states just above the valence band or below the conduction band, respectively. These gap states may contribute to significant changes in the optical and electronic properties of SnO2, thus affecting the metal oxide’s suitability for photovoltaics and photocatalytic devices. In particular, we found that iodine (I) doping of SnO2 induces a high dielectric constant while also reducing the oxide’s bandgap, making it more efficient for light-harvesting applications.

Measurements of Light-Induced Degradation in A-Si, Ge:H, F Alloys,

1986 ◽  
Vol 70 ◽  
Author(s):  
J. Kolodzey ◽  
S. Aljishi ◽  
Z E. Smith ◽  
V. Chu ◽  
R. Schwarz ◽  
...  
Keyword(s):  
Activation Energy ◽  
Electronic Properties ◽  
Dark Conductivity ◽  
Narrow Gap ◽  
Conductivity Activation Energy ◽  
Optical And Electronic Properties ◽  
Amorphous Si

ABSTRACTThe effects of illumination on the optical and electronic properties of narrow gap hydrogenated and fluorinated amorphous Si-Ge (a-Si1-xGex:H, F) alloys have been evaluated. A series of alloys with optical gaps ranging from 1.30 eV to 1.64 eV has been light soaked at ∼1 sun intensity for 354 hours. Measurements of sub-gap absorption, photo- and dark conductivities and dark conductivity activation energy were made on alloys in the annealed and the light-soaked states. The results indicate that samples with optical gaps ≳ 1.4 eV degrade significantly. The 1.3 eV sample shows no degradation in its optical or electronic properties except for a factor of 5 increase in the dark conductivity.

Molecular Dynamics Simulations of the Structural, Vibrational and Electronic Properties of Amorphous Silicon

1990 ◽  
Vol 192 ◽  
Author(s):  
R. Biswas ◽  
I. Kwon ◽  
C. M. Soukoulis
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Amorphous Silicon ◽  
Electronic Properties ◽  
Film Deposition ◽  
Dangling Bond ◽  
Melt Quenching ◽  
Dynamics Simulations ◽  
Si Films ◽  
Gap States

ABSTRACTAmorphous silicon models have been computer-generated by melt-quenching and film deposition molecular dynamics simulations, employing classical interatomic Si-potentials. The structural, vibrational and electronic properties of these models is described. Dangling-bond gap states are well localized whereas, floating bonds gap states are considerably less localized with wavefunction amplitudes on the neighbors of the five-coordinated atom. In contrast to melt-quenched models, the a-Si films displayed voids, a 15–28% lower density than c-Si, and no five- coordinated atoms. A-Si:H models with 5 and 22% hydrogen, and both monohydride and dihydride species, have also been developed.

Substrate Temperature Dependence of the Optical and Electronic Properties of Glow Discharge Produced a-Ge:H

1989 ◽  
Vol 149 ◽  
Author(s):  
Yuan- Min Li ◽  
Warren A. Turner ◽  
Choochon Lee ◽  
William Paul
Keyword(s):  
Glow Discharge ◽  
Substrate Temperature ◽  
Temperature Dependence ◽  
Electronic Properties ◽  
Dark Conductivity ◽  
Index Of Refraction ◽  
Atmospheric Contamination ◽  
Optical And Electronic Properties ◽  
Substrate Temperatures ◽  
Post Deposition

ABSTRACTGlow discharge a-Ge:H films produced at substrate temperatures (Tδ) between 50°C and 350°C, with and without a top a-Si:H capping layer, have been studied. The uncapped samples produced at Tδ < 250°C suffer severe post-deposition atmospheric contamination, resulting in orders of magnitude of unstable increase in both the photoresponse and dark conductivity. The capped samples, which have very much reduced immediate post-deposition contamination, show only small increases in the efficiency-mobility-lifetime product (ŋμτ) with increasing Tδ. This contrasts with the results of earlier similar studies on uncapped samples, which showed a peak in either the photoconductivity1 or the ratio of photoconductivity to dark conductivity2 for 150°C < Tδ < 2000C. We have also observed a decrease in the bandgap, a narrowing of the band-tails, an increase in the index of refraction, and a reduction of hydrogen content of the films with increasing Tδ.

Photocarrier Transport and Recombination in Amorphous Silicon

1993 ◽  
Vol 297 ◽  
Author(s):  
C.R. Wronski ◽  
R.M. Dawson ◽  
M. Gunes ◽  
Y.M. Li ◽  
R.W. Collins
Keyword(s):  
Solar Cell ◽  
Carrier Mobility ◽  
Carrier Transport ◽  
Room Temperature ◽  
Dark Conductivity ◽  
Conductivity Measurements ◽  
Dangling Bond ◽  
Dual Beam ◽  
Temperature Electron ◽  
Gap States

The effect of microstructure in undoped a-Si:H films on carrier transport, recombination, densities of midgap states and solar cell characteristics has been investigated. Extended state mobilities of electrons were obtained from photo and dark conductivity measurements between 40° C and 190° C and the gap states characterized using Dual Beam Photoconductivity. In these films the estimated room temperature electron mobilities increase from about 1 to 30 cm2/V sec as the dihydride concentrations and void volume fractions decrease. It is found that the carrier mobility-lifetime products are not solely determined by the dangling bond states. The effects of changes in the mobilities and midgap states on p-i-n homojunction solar cell characteristics are presented and discussed.

Defects in Amorphous Silicon

1982 ◽  
Vol 14 ◽  
Author(s):  
D. K. Biegelsen
Keyword(s):  
Amorphous Silicon ◽  
Electronic Properties ◽  
Crystalline Silicon ◽  
Random Network ◽  
Optical And Electronic Properties ◽  
Characteristic Features ◽  
Gap States ◽  
Hydrogenated Amorphous ◽  
Silicon Defects ◽  
Continuous Random Network

ABSTRACTIn this paper we argue that amorphous silicon can be treated as a relaxed continuous random network. The optical and electronic properties are controlled by localized gap states which arise from characteristic features of a disordered tetrahedrally-bonded covalent network. Experimental results are reviewed which indicate that the dominant (perhaps only) electrically-active defect in hydrogenated amorphous silicon is the topologically distinct, silicon dangling bond. Finally, we suggest that the same, disorder-related characteristics might also typify the electronic properties of some macroscopic crystalline silicon defects.

Light-induced changes in dark conductivity of Kapton

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

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

1,1’-Biaceanthrylene and 2,2'-Biaceanthrylene: Models for Linking Larger Polycyclic Aromatic Hydrocarbons via Five-Membered Rings

2019 ◽  
Author(s):  
Yachu Du ◽  
Kyle Plunkett
Keyword(s):  
Polycyclic Aromatic Hydrocarbons ◽  
Polycyclic Aromatic Hydrocarbon ◽  
Aromatic Hydrocarbon ◽  
Electronic Properties ◽  
Aromatic Hydrocarbons ◽  
Model Systems ◽  
Redox Potentials ◽  
Dimer Model ◽  
Optical And Electronic Properties ◽  
Polycyclic Aromatic

We show that polycyclic aromatic hydrocarbon (PAH) chromophores that are linked between two five-membered rings can access planarized structures with reduced optical gaps and redox potentials. Two aceanthrylene chromophores were connected into dimer model systems with the chromophores either projected outward (2,2’-biaceanthrylene) or inward (1,1’-biaceanthrylene) and the optical and electronic properties were compared. Only the planar 2,2’-biaceanthrylene system showed significant reductions of the optical gaps (1 eV) and redox potentials in relation to the aceanthrylene monomer.<br>

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