Persistent Photoinduced Changes in Charge States of Donors and Acceptors in Hydrothermally Grown ZnO

2006 ◽  
Vol 957 ◽  
Author(s):  
Nancy C. Giles ◽  
Yongquan Jiang ◽  
Xiaocheng Yang ◽  
S. M. Evans ◽  
L. E. Halliburton
Keyword(s):  
Charge Trapping ◽  
Paramagnetic Resonance ◽  
Group Iii ◽  
Device Structures ◽  
State Changes ◽  
Charge States ◽  
The Stability ◽  
Photoinduced Changes ◽  
Electron Paramagnetic ◽  
Dominant Acceptor

ABSTRACTBulk ZnO grown by the hydrothermal technique was investigated using electron paramagnetic resonance (EPR), photoluminescence (PL), and infrared absorption (FTIR) techniques. Isolated subsitutional lithium is the dominant acceptor and could be detected using EPR or PL. A large concentration of neutral Li+-OH− centers were observed using FTIR data. EPR spectra assigned to Mn, Co, Ni, Fe, and Group III (Al, Ga) donors were also observed. Photoinduced changes in the charge states of the different deep and shallow centers were produced using 325 nm light, and the stability of these changes were monitored with EPR during pulsed thermal anneals. The charge-state changes for some defects were persistent and remained up to 300 K. These impurities, when present in device structures, may act as stable charge trapping sites.

Intrinsic Defects in HPSI 6H-SiC: an EPR Study

2008 ◽  
Vol 600-603 ◽  
pp. 381-384 ◽  
Author(s):  
Patrick Carlsson ◽  
Nguyen Tien Son ◽  
Björn Magnusson ◽  
Anne Henry ◽  
Erik Janzén
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Vapor Deposition ◽  
Thermal Activation ◽  
Chemical Vapor ◽  
Paramagnetic Resonance ◽  
Intrinsic Defects ◽  
Annealing Behavior ◽  
Carbon Vacancy ◽  
The Stability ◽  
Electron Paramagnetic

High-purity, semi-insulating 6H-SiC substrates grown by high-temperature chemical vapor deposition were studied by electron paramagnetic resonance (EPR). The carbon vacancy (VC), the carbon vacancy-antisite pair (VCCSi) and the divacancy (VCVSi) were found to be prominent defects. The (+|0) level of VC in 6H-SiC is estimated by photoexcitation EPR (photo-EPR) to be at ~ 1.47 eV above the valence band. The thermal activation energies as determined from the temperature dependence of the resistivity, Ea~0.6-0.7 eV and ~1.0-1.2 eV, were observed for two sets of samples and were suggested to be related to acceptor levels of VC, VCCSi and VCVSi. The annealing behavior of the intrinsic defects and the stability of the SI properties were studied up to 1600°C.

Charge Trapping Centers in Ferroelectric Ceramics

1992 ◽  
Vol 284 ◽  
Author(s):  
C. H. Seager ◽  
W. L. Warren ◽  
B. A. Tuttle ◽  
R. D. Nasby ◽  
D. Dimos
Keyword(s):  
Uv Light ◽  
Charge Trapping ◽  
Ferroelectric Ceramics ◽  
Electrical Measurements ◽  
Lead Lanthanum Zirconate Titanate ◽  
Paramagnetic Resonance ◽  
Lanthanum Zirconate ◽  
Polarization Electric Field ◽  
Crystal Field Parameters ◽  
Electron Paramagnetic

ABSTRACTElectron paramagnetic resonance (EPR), photo-thermal deflection spectroscopy (PDS), and electrical measurements have been used to characterize as-received and UV-lluminated lead lanthanum zirconate titanate (PLZT) and PZT ceramics. Following optical illumination we observe the activation of positively charged Pb+3 and negatively charged Ti+3 ions, as well as an increased broad absorption peak around 2.6 eV. The spatial distribution of the induced absorption correlates well with the location of the absorbed UV, suggesting that photo-produced carrier pairs are trapped at Ti+4 and Pb+2 producing the observed paramagnetism. The Ti+3 EPR spectra were successfully fit using the crystal field parameters derived from the PDS spectra. Preliminary results suggest that these charged paramagnetic ions can influence the electrical properties of PZT thin films. We investigated the effects of UV light and dc bias sequences by polarization-electric field (PE) measurements and find that the coercive fields are dependent on the sign of the applied bias during UV exposure. It is reasonable to expect that Pb+3 and/or Ti+3 ions act as the charge trapping sites which cause the threshold voltage shifts in the PE loop.

scholarly journals Activation of Cadmium Under Simulated Solar Illumination and Its Impact on the Mobility of Cd in Flooded Soils

2021 ◽  
Author(s):  
Bihao Luo ◽  
Chenfeng Xiao ◽  
Yuling Liu ◽  
Li Li ◽  
Liang Peng ◽  
...  
Keyword(s):  
Fold Increase ◽  
Environmental Water ◽  
Solar Irradiation ◽  
Natural Soil ◽  
Release Kinetic ◽  
Flooded Soils ◽  
Paramagnetic Resonance ◽  
Water Ph ◽  
The Stability ◽  
Electron Paramagnetic

Abstract In waterlogged paddy soils, cadmium (Cd) can be precipitated as cadmium sulfide (CdS) under reductive environment, thereby limiting the absorption of Cd by plants. Multiple environmental factors (such as water, pH, Eh, etc.) played a role in the control of Cd mobility and bioavailability. In this study, we investigated the influence of the solar irradiation on the photo-dissolution of synthetic CdS-montmorillonite composites (CdS-M) in solution and the stability of Cdin natural soil. The release kinetic of Cd2+ showed that after the irradiation of simulated sunlight, CdS-M composites became less stable compared to the dark control. The solar irradiation seemed to enhance the release of Cd2+ from CdS significantly and continuously. Electron paramagnetic resonance (EPR) and quenching experiments confirmed that the photogenerated holes, O2·- and •OH were possibly involved in the photo-induced release of Cd2+, while the holes was primarily responsible for the reaction.Irradiation under alkaline solution or the presence of DOM, PO43-, CO32- and urea markedly inhibited the photodissolution process of CdS. The photo-mediated activation of Cd was further confirmed in paddy soil under natural sunlight, with a nearly 3-fold increase in concentration of extractable Cd during the 15 days irradiation. This study highlights the importance of photochemical transformation of Cd in the environmental water and soil.

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF (VO4)+2 IONS DOPED IN REDUCED Pb10-xCax(VO4)1(PO4)5(OH)2 APATITES [x = 0.0, 2.0, 4.0, 6.0, 8.0, AND 10.0]

2009 ◽  
Vol 23 (16) ◽  
pp. 3369-3389
Author(s):  
M. IKRAM ◽  
R. AMBARDAR ◽  
A. M. ROSSI ◽  
J. G. EON
Keyword(s):  
Esr Spectroscopy ◽  
Lattice Relaxation ◽  
Esr Spectra ◽  
Hydrogen Gas ◽  
Spin Lattice Relaxation ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
The Stability ◽  
Calcium Doping ◽  
Electron Paramagnetic

Polycrystalline solid solution of phosphate and vanadate lead calcium apatites Pb 10 -x Ca x( VO 4)1( PO 4)5( OH )2 apatites [x = 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0] was reduced with hydrogen gas at the temperature of 300 and 400°C for 1 h. All these compounds were investigated by XRD and ESR spectroscopy. Only one reduced oxidation state V +4 was detected. Two types of species like isolated vanadium (+4) and clusters of V 4+ had been observed. The stability of the apatites increases and the particle size of the crystal decreases with calcium doping concentrations. As the concentrations of Ca increase the intensity of ESR lines deviates due to the spin–lattice relaxation interactions. The deviation in the intensity of ESR spectra can be attributed as the coexistence of paramagnetic and antiferromagnetic phases in the apatites.

Spectroscopy of Transition-Metal-Hydrogen Complexes in Silicon

1995 ◽  
Vol 378 ◽  
Author(s):  
Michael Stavola ◽  
S.J. Uftring ◽  
M.J. Evans ◽  
P.M. Williams ◽  
G.D. Watkins
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electrical Properties ◽  
Transition Metal ◽  
Charge State ◽  
Vibrational Spectroscopy ◽  
Structural Information ◽  
Paramagnetic Resonance ◽  
Charge States ◽  
Electron Paramagnetic

AbstractTransition-metal-hydrogen complexes have been introduced into bulk Si samples that contained Pt, Au, or Rh by the indiffusion of hydrogen at 1250°C from H2 gas. The structure and electrical properties of a PtH2 complex in Si have been studied by vibrational spectroscopy and electron paramagnetic resonance (EPR). The PtH2 complex has been found to introduce two levels in the Si bandgap. There is one paramagnetic charge state for which EPR provides detailed structural information and two nonparamagnetic charge states. The hydrogen vibrations of all three charge states of PtH2 have been assigned. In addition to the PtH2 complex, the hydrogen vibrations of several additional complexes in Si samples that contain hydrogen and Pt, Au, or Rh have been identified.

Sign in / Sign up

Export Citation Format

Share Document