Defect Relaxation in a-Si:H Studied by Defect Absorption and Luminescence

1993 ◽  
Vol 297 ◽  
Author(s):  
Daxing Han ◽  
Yang Xiao
Keyword(s):  
Band Gap ◽  
Photon Emission ◽  
Forward Bias ◽  
Emission Spectra ◽  
Energy Position ◽  
Bias Effect ◽  
Band Absorption ◽  
Capacitance Transient ◽  
Defect Relaxation ◽  
Transient Measurements

The experimental results about defect relaxation in a-Si:H have been reported recently on several transient measurements, such as forward-bias-transient-current,1 optical bias effect on electron drift,2 and photo-capacitance transient.3 In this paper we report the steady state results of the bias effect on sub-band-gap absorption and photon-emission spectra measurements in undoped samples.The optical bias effects the sub-band absorption. In additional to an enhancement of the sub-band gap absorption, the absorption threshold moved from 0.8 eV to 0.6 eV for undoped samples under optical bias at room temperature. The effects are larger in the light-soaked-state than in the annealed-state.We also report on the generation rate dependence on photoluminescence (PL) spectra line shape. We found that the energy position of the defect PL band shifted from 1.1 eV to 0.9 eV when the excitation level increased 4,000 times.While motion of the quasi-Fermi level as a explanation cannot be eliminated, defect relaxation seems more plausible.

Observation of Configurational Switching of Deep Defects in a-Si:H Using Thermal Step Insertion During Capacitance Transient Measurements

1996 ◽  
Vol 420 ◽  
Author(s):  
Adam D. Gardner ◽  
J. David Cohen
Keyword(s):  
Thermal Emission ◽  
Full Range ◽  
Type A ◽  
Defect States ◽  
The Many ◽  
Capacitance Transient ◽  
Defect Relaxation ◽  
Transient Measurements ◽  
Temperature Switch ◽  
Emission Phase

AbstractIn standard, isothermal capacitance transient measurements, configurational changes in defect states are normally very difficult to identify because, depending on the relative rates of thermal emission to the configurational relaxation, charge will be emitted predominantly from only one configuration. We have found, however, that employing a thermal step during the emission phase of the transient enhances the effect of defect relaxation; one can then observe the resultant switch between distinct configurations. We have applied this method quite successfully to lightly doped n-type a-Si:H samples by varying the overall temperature (between 270K and 350K) and the magnitude of the temperature switch (from 20K to 35K). For the smallest temperature steps, the resultant transients suggest two distinct configurations that, we believe, reflect only a fraction of the many latent configurations that account for the full range of relaxation possible.

Capacitance Characterization of Amorphous Silicon/Amorphous Silicon Germanium Heterostructures

1996 ◽  
Vol 420 ◽  
Author(s):  
C. Palsule ◽  
U. Paschen ◽  
J. D. Cohen ◽  
J. Yang ◽  
S. Guha
Keyword(s):  
Amorphous Silicon ◽  
Silicon Germanium ◽  
Crystalline Silicon ◽  
Slow Component ◽  
Forward Bias ◽  
P Type ◽  
Capacitance Transient ◽  
Amorphous Silicon Germanium ◽  
Transient Measurements

AbstractWe have performed voltage-pulse stimulated capacitance transient measurements along with other junction capacitance measurements on a-Si:H/ a-Si,Ge:H heterostructures deposited on p-type crystalline silicon using the glow discharge technique. For a filling pulse that puts the c-Si/a-Si:H junction in forward bias, the capacitance transients consist of two components- a fast component corresponding to electron emission and a slow component corresponding to hole emission. For a fixed starting reverse bias, we have found that the density of trapped holes is proportional to the product of the filling pulse voltage and the filling pulse width and reaches a saturation value at a certain value of the product. These hole traps appear to reside at or very close to the a-Si:H/a-Si,Ge:H interface. The estimated trap concentration is around 1011/cm2 and is independent of temperature and applied bias, ruling out the creation of the traps during the filling pulse. We also report results on samples in which a-Si:H/ a-Si,Ge:H interface has been modified during growth to alter the concentration of the hole traps.

scholarly journals Influence of Calcination Temperature on Crystal Growth and Optical Characteristics of Eu3+ Doped ZnO/Zn2SiO4 Composites Fabricated via Simple Thermal Treatment Method

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 115
Author(s):  
Suhail Huzaifa Jaafar ◽  
Mohd Hafiz Mohd Zaid ◽  
Khamirul Amin Matori ◽  
Sidek Hj. Ab Aziz ◽  
Halimah Mohamed Kamari ◽  
...  
Keyword(s):  
Thermal Treatment ◽  
Band Gap ◽  
Calcination Temperature ◽  
Emission Intensity ◽  
Emission Spectra ◽  
Treatment Method ◽  
Absorption Bands ◽  
Vis Spectroscopy ◽  
Doped Zno ◽  
Zno Crystal

This research paper proposes the usage of a simple thermal treatment method to synthesis the pure and Eu3+ doped ZnO/Zn2SiO4 based composites which undergo calcination process at different temperatures. The effect of calcination temperatures on the structural, morphological, and optical properties of ZnO/Zn2SiO4 based composites have been studied. The XRD analysis shows the existence of two major phases which are ZnO and Zn2SiO4 crystals and supported by the finding in the FT-IR. The FESEM micrograph further confirms the existence of both ZnO and Zn2SiO4 crystal phases, with progress in the calcination temperature around 700–800 °C which affects the existence of the necking-like shape particle. Absorption humps discovered through UV-Vis spectroscopy revealed that at the higher calcination temperature effects for higher absorption intensity while absorption bands can be seen at below 400 nm with dropping of absorption bands at 370–375 nm. Two types of band gap can be seen from the energy band gap analysis which occurs from ZnO crystal and Zn2SiO4 crystal progress. It is also discovered that for Eu3+ doped ZnO/Zn2SiO4 composites, the Zn2SiO4 crystal (5.11–4.71 eV) has a higher band gap compared to the ZnO crystal (3.271–4.07 eV). While, for the photoluminescence study, excited at 400 nm, the emission spectra of Eu3+ doped ZnO/Zn2SiO4 revealed higher emission intensity compared to pure ZnO/Zn2SiO4 with higher calcination temperature exhibit higher emission intensity at 615 nm with 700 °C being the optimum temperature. The emission spectra also show that the calcination temperature contributed to enhancing the emission intensity.

Optical Properties and Zinc Nitride Thin Films Prepared Using Magnetron Reactive Sputtering

2014 ◽  
Vol 940 ◽  
pp. 11-15
Author(s):  
Jun Qin Feng ◽  
Jun Fang Chen
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Near Infrared ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Sem Images ◽  
Fluorescence Emission Spectra ◽  
Glass Substrates ◽  
Zinc Nitride ◽  
Direct Band

Zinc nitride films were deposited by ion sources-assisted magnetron sputtering with the use of Zn target (99.99% purity) on 7059 glass substrates. The films were characterized by XRD, SEM and EDS, the results of which show that the polycrystalline zinc nitride thin film can be grown on the glass substrates, the EDS spectrum confirmed the chemical composition of the films and the SEM images revealed that the zinc nitride thin films have a dense structure. Ultraviolet-visible-near infrared spectrophotometer was used to study the transmittance behaviors of zinc nitride thin films, which calculated the optical band gap by Davis Mott model. The results of the fluorescence emission spectra show the zinc nitride would be a direct band gap semiconductor material.

Band-Gap Energy Dependence of Emission Spectra in Rare Earth-Doped Zn(1-x)CdxS Thin Film Electroluminescent Devices

1992 ◽  
Vol 31 (Part 1, No. 2A) ◽  
pp. 295-300 ◽  
Author(s):  
Noboru Miura ◽  
Takashi Sasaki ◽  
Hironaga Matsumoto ◽  
Ryotaro Nakano
Keyword(s):  
Thin Film ◽  
Rare Earth ◽  
Band Gap ◽  
Energy Dependence ◽  
Emission Spectra ◽  
Band Gap Energy ◽  
Electroluminescent Devices ◽  
Gap Energy ◽  
Rare Earth Doped

scholarly journals Efficiency of tunable band-gap structures for single-photon emission

2004 ◽  
Vol 69 (6) ◽  
Author(s):  
Ho Trung Dung ◽  
Ludwig Knöll ◽  
Dirk-Gunnar Welsch
Keyword(s):  
Band Gap ◽  
Single Photon ◽  
Photon Emission ◽  
Single Photon Emission ◽  
Tunable Band Gap

Effect of Contacts on Capacitance Transient Measurements in N-Type Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
W. B. Jackson ◽  
N. M. Johnson ◽  
J. Walker
Keyword(s):  
Amorphous Silicon ◽  
Pulse Duration ◽  
Ohmic Contacts ◽  
Hydrogenated Amorphous Silicon ◽  
Charge Injection ◽  
Current Injection ◽  
Anomalous Dependence ◽  
Capacitance Transient ◽  
Hydrogenated Amorphous ◽  
Transient Measurements

ABSTRACTMeasurement of the dependence of emission capacitance transients on filling pulse duration has been extended to devices with Ohmic back contacts. Capacitance transients on devices possessing identical bulk 20-ppm P doped a-Si:H but either Ohmic contacts or blocking contacts were compared. The devices with blocking contacts completely reproduced in quantitative detail the previously observed anomalous dependence of capacitance transients on filling pulse duration. The diodes with Ohmic contacts showed no evidence of the anomalous filling pulse effect even for light-degraded, resistive samples. Current injection measurements show that blocking contacts delay the charge injection into the device by about 10–100 msec.

Luminescence of II-VI Semiconductor Nanoparticles

2014 ◽  
Vol 222 ◽  
pp. 1-65 ◽  
Author(s):  
B.P. Chandra ◽  
V.K. Chandra ◽  
Piyush Jha
Keyword(s):  
Band Gap ◽  
Data Storage ◽  
Quantum Confinement Effect ◽  
Ultrafine Particle ◽  
Surface States ◽  
Emission Spectra ◽  
Volume Ratio ◽  
Blue Shift ◽  
Band Gap Energy ◽  
Molecular Engineering

Nanoparticle or an ultrafine particle is a small solid whose physical dimension lies between 1 to 100 nanometers. Nanotechnology is the coming revolution in molecular engineering, and therefore, it is curiosity-driven and promising area of technology. The field of nanoscience and nanotechnology is interdisciplinary in nature and being studied by physicists, chemists, material scientists, biologists, engineers, computer scientists, etc. Research in the field of nanoparticles has been triggered by the recent availability of revolutionary instruments and approaches that allow the investigation of material properties with a resolution close to the atomic level. Strongly connected to such technological advances are the pioneering studies that have revealed new physical properties of matter at a level intermediate between atomic/molecular and bulk. Quantum confinement effect modifies the electronic structure of nanoparticles when their sizes become comparable to that of their Bohr excitonic radius. When the particle radius falls below the excitonic Bohr radius, the band gap energy is widened, leading to a blue shift in the band gap emission spectra, etc. On the other hand, the surface states play a more important role in the nanoparticles, due to their large surface-to-volume ratio with a decrease in particle size (surface effects). From the last few years, nanoparticles have been a common material for the development of new cutting-edge applications in communications, energy storage, sensing, data storage, optics, transmission, environmental protection, cosmetics, biology, and medicine due to their important optical, electrical, and magnetic properties.

The Role of Deep Defect Relaxation Dynamics in Optical Processes in Hydrogenated Amorphous Silicon

1995 ◽  
Vol 377 ◽  
Author(s):  
Fan Zhong ◽  
J. David Cohen
Keyword(s):  
Relaxation Dynamics ◽  
Energy Position ◽  
Defect Band ◽  
Transient Photoconductivity ◽  
Photoconductivity Decay ◽  
Long Time ◽  
Intimate Relation ◽  
Hydrogenated Amorphous ◽  
Defect Relaxation

ABSTRACTWe report results of a transient modulated photocurrent technique which allows us to observe the time evolution of the D0 sub-band under the application of optical bias light and after turning off this bias light Our measurements show that the D0 band shifts monotonically to shallower thermal energies after the bias light is applied, with roughly 10 seconds to saturation at 300K and to deeper thermal energies after removing the bias light, with a decay time of over 1000 seconds. We have also found there exists an intimate relation between the motion of the D0 band and that of the quasi Fermi level as deduced from the transient photoconductivity and therefore, in particular, to the long time photoconductivity decay. This relation is exactly reproduced by the assumption of a D0 band whose energy position evolves in time, together with a recombination process dominated by changes in the charge state of a deeper defect band under light bias.

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