scholarly journals Persistent Photoconductivity in ZnO Nanowires in Different Atmospheres

2014 ◽  
Vol 2014 ◽  
pp. 1-5 ◽  
Author(s):  
Davide Cammi ◽  
Carsten Ronning
Keyword(s):  
Conduction Band ◽  
Inert Gas ◽  
Persistent Photoconductivity ◽  
Zno Nanowire ◽  
Reduced Pressure ◽  
Band Bending ◽  
Proposed Model ◽  
Photo Conductivity ◽  
Nanowire Device ◽  
Uv Excitation

We investigated the photoconductivity of single ZnO nanowire device as a function of the surrounding atmosphere, considering the comparison between reduced pressure, inert gas environments, and air. We show that after UV excitation the photocurrent persists for hours, in particular in vacuum, nitrogen, and argon. In the presence of oxygen, the photodecay rate is initially fast but then becomes considerably slower, resulting in a long persisting photo-conductivity tail. Our proposed model explains the persistence of the photoconductivity (PPC) in terms of band bending at the surface of the nanowires, which is related to the trapping of electrons from the conduction band.

Persistent Photoconductivity And Thermal Recovery Kinetics Of Low Energy Ar + Bombarded GaAs

1991 ◽  
Vol 223 ◽  
Author(s):  
A. Vaseashta ◽  
L. C. Burton
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Thermal Recovery ◽  
Low Energy ◽  
Persistent Photoconductivity ◽  
Transport Parameters ◽  
Excellent Correlation ◽  
Proposed Model ◽  
Transient Spectroscopy ◽  
Kinetics Of

ABSTRACTKinetics of persistent photoconductivity, photoquenching, and thermal and optical recovery observed in low energy Ar+ bombarded on (100) GaAs surfaces have been investigated. Rate and transport equations for these processes were derived and simulated employing transport parameters, trap locations and densities determined by deep level transient spectroscopy. Excellent correlation was obtained between the results of preliminary simulation and the experimentally observed values. The exponential decay of persistent photoconductivity response curve was determined to be due to metastable electron traps with longer lifetime and is consistent with an earlier proposed model.

scholarly journals Low-Cost, Large-Area, Facile, and Rapid Fabrication of Aligned ZnO Nanowire Device Arrays

2016 ◽  
Vol 8 (21) ◽  
pp. 13466-13471 ◽  
Author(s):  
Gerard Cadafalch Gazquez ◽  
Sidong Lei ◽  
Antony George ◽  
Hemtej Gullapalli ◽  
Bernard A. Boukamp ◽  
...  
Keyword(s):  
Low Cost ◽  
Zno Nanowire ◽  
Large Area ◽  
Rapid Fabrication ◽  
Nanowire Device

scholarly journals Enhancing ultraviolet photoresponse of ZnO nanowire device by surface functionalization

2008 ◽  
Vol 57 (12) ◽  
pp. 7855
Author(s):  
Huang Jin-Hua ◽  
Zhang Kun ◽  
Pan Nan ◽  
Gao Zhi-Wei ◽  
Wang Xiao-Ping
Keyword(s):  
Surface Functionalization ◽  
Zno Nanowire ◽  
Nanowire Device

Enhancement of persistent photoconductivity by uv excitation in GdBa2Cu3O6.3

1996 ◽  
Vol 54 (6) ◽  
pp. R3750-R3752 ◽  
Author(s):  
T. Endo ◽  
A. Hoffmann ◽  
J. Santamaria ◽  
Ivan K. Schuller
Keyword(s):  
Persistent Photoconductivity ◽  
Uv Excitation

scholarly journals A Photocapture Test of DX-Center Models

1989 ◽  
Vol 163 ◽  
Author(s):  
Harold P. Hjalmarson ◽  
S. R. Kurtz ◽  
T. M. Brennan
Keyword(s):  
Conduction Band ◽  
Cross Section ◽  
Threshold Energy ◽  
Photoionization Cross Section ◽  
Persistent Photoconductivity ◽  
Dx Centers ◽  
Null Result ◽  
Dx Center

AbstractThe DX-center model is widely used to explain data for the persistent photoconductivity (PPC) effect. An analysis of the DX-center model suggests a new experiment to test its correctness. In this experiment, photons near the threshold energy of the photoionization cross-section for the DX-center induce transitions from the partially occupied conduction band to empty DX-centers. This mechanism, which we call photocapture, competes with the usual photoionization which empties the DX-centers. The photocapture cross-section is estimated and an experimental attempt is made to detect photocapture. The significance of the null result is discussed.

Photoconductive behavior of binary porphyrin crystalline assemblies

2017 ◽  
Vol 21 (09) ◽  
pp. 569-580 ◽  
Author(s):  
Bryan Borders ◽  
Morteza Adinehnia ◽  
Naomi Rosenkrantz ◽  
Marshall van Zijll ◽  
K. W. Hipps ◽  
...  
Keyword(s):  
Laser Light ◽  
Soret Band ◽  
Charge Carriers ◽  
Water Molecules ◽  
Persistent Photoconductivity ◽  
Temperature Dependent ◽  
Recombination Mechanism ◽  
Laser Illumination ◽  
Proposed Model ◽  
Illumination Wavelength

The mechanism of photoconductivity in a crystalline photoconductor synthesized from 1:1 ratio of meso-tetra(4-pyridyl)porphyrin (TPyP) and meso-tetra(4-sulfonatophenyl)porphyrin (TSPP) ionic tectons was examined. The rod-like crystals of TPyP:TSPP insulate in the dark but become photoconducting on illumination and a portion of the photoinduced current persists after the laser light is turned off. This persistent photoconductivity (PPC) is investigated as a function of laser illumination wavelength, laser power, and sample temperature. The primary charge carriers in the TPyP:TSPP upon photoexcitation are electrons and the charge recombination mechanism follows monomolecular kinetics. The number of electrons contributing to the photocurrent is directly proportional to the number of photons absorbed thus, the mechanisms of the photoconductivity resulting from excitations within the Soret band and the Q-band are the same. The PPC is interpreted to be the result of the formation of photoinduced metastable defects that allow for Miller–Abrahams-like hopping conductivity. The TPyP:TSPP has an incommensurately modulated crystal lattice and its proposed model structure is based on both ionic and neutral porphyrin tectons. The thermogravimetric analysis shows that the porphyrin crystals undergo dehydration on heating (˜50 ∘C) by losing water molecules located in the crystalline channels. Temperature dependent XRD indicates that dehydration causes irreversible changes to the crystal structure. The loss of crystallinity observed with heating the TPyP:TSPP crystals above 90 ∘C causes approximately 25% loss in photoconductivity but has little effect on the lifetime associated with the persistent photoconductivity.

Physical model for the exotic ultraviolet photo-conductivity of ZnO nanowire films

2013 ◽  
Vol 22 (11) ◽  
pp. 118102 ◽  
Author(s):  
Yue-Wu Pan ◽  
Shou-Tian Ren ◽  
Shi-Liang Qu ◽  
Qiang Wang
Keyword(s):  
Physical Model ◽  
Zno Nanowire ◽  
Photo Conductivity

Improved Properties of a-SiC:H Alloys with Reduced Density of CH3 Radicals

1992 ◽  
Vol 258 ◽  
Author(s):  
S. S. Camargo ◽  
M. L. de Oliveira ◽  
A. A. Pasa ◽  
C. Gatts
Keyword(s):  
Refractive Index ◽  
Fermi Level ◽  
Carbon Content ◽  
Conduction Band ◽  
Conductivity Measurements ◽  
Hydrogen Atoms ◽  
Optical Gap ◽  
Hydrogen Dilution ◽  
Photo Conductivity ◽  
Reduced Density

ABSTRACTIn this paper we report on the properties of a-SiC:H alloys with reduced density of CH3 radicals obtained by hydrogen dilution of gases. A reduced density of voids, hydrogen content and density of carbon bonded hydrogen atoms, were obtained; while carbon content and density of Si-H bonds are not affected much. A reduction of the optical gap and an increase of the refractive index were observed and related to the reduced densities of CH3 groups and voids. Dark- and photo- conductivity measurements showed that a performance comparable to the best undiluted films may be easily achieved, associated with a shift of the dark Fermi level towards the conduction band.

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