共查询到20条相似文献,搜索用时 31 毫秒
1.
Gangqiang Zha Wanqi Jie Dongmei Zeng Xuxu Bai Wenhua Zhang 《Applied Surface Science》2006,252(24):8421-8423
Angle-resolved photoemission spectroscopy (ARPES) was used to characterize the surface state of clean CdZnTe (1 1 0) surface. The surface state of CdZnTe with the peak at 0.9 eV below the Fermi level is identified. Meanwhile, Photoluminescence (PL) spectrum confirmed that there existed a surface trap state which introduced a deep-level peak at 1.510 eV. The surface trap states can be decreased by aging in dry-air. The surface leakage current was measured also by I-V measurements. After aging, the leakage current was decreased remarkably, which suggested that the aging treatment is an effective method to decrease the surface trap state. 相似文献
2.
This paper investigates the electronic relaxation of deep bulk trap and interface state in ZnO ceramics based on dielectric spectra measured in a wide range of temperature, frequency and bias, in addition to the steady state response. It discusses the nature of net current flowing over the barrier affected by interface state, and then obtains temperature-dependent barrier height by approximate calculation from steady I--V (current--voltage) characteristics. Additional conductance and capacitance arising from deep bulk trap relaxation are calculated based on the displacement of the cross point between deep bulk trap and Fermi level under small AC signal. From the resonances due to deep bulk trap relaxation on dielectric spectra, the activation energies are obtained as 0.22 eV and 0.35 eV, which are consistent with the electronic levels of the main defect interstitial Zn and vacancy oxygen in the depletion layer. Under moderate bias, another resonance due to interface relaxation is shown on the dielectric spectra. The DC-like conductance is also observed in high temperature region on dielectric spectra, and the activation energy is much smaller than the barrier height in steady state condition, which is attributed to the displacement current coming from the shallow bulk trap relaxation or other factors. 相似文献
3.
Electronic properties and deep level transient spectroscopy of CdS/CdTe thin film solar cells 下载免费PDF全文
It is well known that preparing temperatures and defects are highly related to deep-level impurities. In our studies, the CdTe polycrystalline films have been prepared at various temperatures by close spaced sublimation (CSS). The different preparing temperature effects on CdS/CdTe solar cells and deep-level impurities have been investigated by I--V and C--V measurements and deep level transient spectroscopy (DLTS). By comparison, less dark saturated current density, higher carrier concentration, and better photovoltaic performance are demonstrated in a 580oC sample. Also there is less deep-level impurity recombination, because the lower hole trap concentration is present in this sample. In addition, three deep levels, Ev+0.341 eV(H4), Ev+0.226 eV(H5) and EC-0.147 eV(E3), are found in the 580oC sample, and the possible source of deep levels is analysed and discussed. 相似文献
4.
I. Satoh T. Kobayashi K. Katayama T. Okada T. Itoh 《Applied Physics A: Materials Science & Processing》2004,79(4-6):1445-1447
The magneto-photoluminescence (PL) of novel magnetic semiconductor Zn1-xCrxO (ZCO) grown by the pulsed laser deposition (PLD) method was investigated. An ArF excimer laser and Cr2O3-mixed ZnO ceramic bulk targets were used for the PLD experiments. The PL peaks at room temperature are very sharp and there is no deep-level emission. The bound exciton peak at 4.2 K was very sharp and increased about three times with increasing applied magnetic field up to 1 T, and the peak wavelength was slightly blue-shifted. It is admirable that the magneto-PL peak was considerably modulated even at low magnetic field. From the peak shift energy of the magneto-PL, E, effective Cr concentration xeff was roughly estimated to be 0.001 on the basis of the electron (n)-type bound magnetic polaron (BMP) model. PACS 78.55.Et; 78.20.Ls; 75.30.Hx 相似文献
5.
Hot electron dynamics was investigated, with a focus on scattering between bulk states and the C1 surface state that is formed on the (2×4)-reconstructed In-rich surface of InP(100). The latter surface was prepared via metal organic chemical vapor deposition (MOCVD) and monitored by reflectance anisotropy spectroscopy (RAS/RDS). Two-color twophoton photoemission (2PPE) was employed with laser pulses of about 50 fs duration. Hot electrons were generated in bulk states about 0.5 eV above the C1 surface state, thereby avoiding any significant direct optical population of the surface state. A time constant of 35 fs was determined from the experimental data for electron scattering from isoenergetic bulk states to the C1 surface state by analyzing the rise of a C1-specific peak in the 2PPE spectrum. The decay of this C1 peak was ascribed to energy relaxation of the photo-generated electrons to bulk states below the surface state. Analogous measurements were carried out with a (2×1/2×2)-reconstructed P-rich surface of InP(100) that was also grown via MOCVD. No sign of a surface statewas detected in the 2PPE spectra for the latter surface in the corresponding energy range of the conduction band. PACS 73.20.-r; 78.47.+p; 79.60.-i; 79.60.Bm 相似文献
6.
7.
S. Kaschieva K.G. Stefanov D. Karpuzov 《Applied Physics A: Materials Science & Processing》1998,66(5):561-563
2 structures implanted with 50-keV boron ions is studied by deep-level transient spectroscopy (DLTS) measurements. The DLTS
spectra of ion-implanted samples exhibit one peak which corresponds to a deep level located in the forbidden gap of the silicon
matrix at Ec-0.40 eV below the conducting band edge. New additional shallower levels are found in the spectra following bombardment by
high-energy electrons, the peak intensity being dependent on the irradiation dose. The corresponding activation energy of
the created defects, the density of the traps, and the electron-capture cross sections are evaluated.
Received: 27 October 1997/Accepted: 8 December 1997 相似文献
8.
Photoluminescence excitation (PLE) spectra of deep acceptor states in ZnSe, for example the Cu-related luminescence band at ≈1.95 eV, contain a prominent excitation band at ≈3.25 eV. This band lies above the structure marking the lowest direct EO band gap Eg by the spin-orbit splitting energy Δ of the valence bands at Γ. The higher energy feature is either absent or greatly de-emphasised in the PLE spectra of shallow acceptor states in ZnSe and of the oxygen iso-electronic trap in ZnTe, where the electron rather than the hole is tightly bound. However, a significant PLE component at Eg + Δ is observed for deep acceptor-like states in ZnTe, where Δ is ≈0.95 eV. Efficient PLE at E + Δ for luminescence from deep acceptor-like states is shown to be consistent with the extended wave-vector contributions to the bound state wave-functions of holes of binding energies ≈Δ. 相似文献
9.
P.N.K. Deenapanray H.H. Tan C. Jagadish 《Applied Physics A: Materials Science & Processing》2003,76(6):961-964
Defects created in rapid thermally annealed n-GaAs epilayers capped with native oxide layers have been investigated using
deep-level transient spectroscopy (DLTS). The native oxide layers were formed at room temperature using pulsed anodic oxidation.
A hole trap H0, due to either interface states or injection of interstitials, is observed around the detection limit of DLTS
in oxidized samples. Rapid thermal annealing introduces three additional minority-carrier traps H1 (EV+0.44 eV), H2 (EV+0.73 eV), and H3 (EV+0.76 eV). These hole traps are introduced in conjunction with electron traps S1 (EC-0.23 eV) and S2 (EC-0.45 eV), which are observed in the same epilayers following disordering using SiO2 capping layers. We also provide evidence that a hole trap whose DLTS peak overlaps with that of EL2 is present in the disordered
n-GaAs layers. The mechanisms through which these hole traps are created are discussed. Capacitance–voltage measurements reveal
that impurity-free disordering using native oxides of GaAs produced higher free-carrier compensation compared to SiO2 capping layers.
Received: 12 March 2002 / Accepted: 15 July 2002 / Published online: 22 November 2002
RID="*"
ID="*"Corresponding author. Fax: +61-2/6125-0381, E-mail: pnk109@rsphysse.anu.edu.au 相似文献
10.
利用同步辐射角分辨光电子能谱(SRARPES)对6H-SiC(0001)-6[KF(]3[KF)]×6[KF(]3[KF)] R30°重构表面的电子结构和表面态进行了研究.通过鉴别价带谱中来自于体态的信息,可以推断出重构表面的费米能级位于体态价带顶之上(2.1±0.1)eV处.实验测出的体能带结构与理论计算的结果较为符合.在重构表面上发现三个表面态,分别位于结合能-0.48 eV(S0),-1.62 eV(S1)和-4.
关键词:
角分辨光电子能谱
碳化硅(SiC)
电子结构
表面态 相似文献
11.
Adrie J.J. Bos Nigel R.J. Poolton Jakob Wallinga Aurélie Bessière Pieter Dorenbos 《Radiation measurements》2010,45(3-6):343-346
Energy-resolved optically stimulated luminescence (OSL) spectra and thermoluminescence (TL) glow curves of a powder sample of YPO4:Ce3+,Sm3+ were measured to investigate the nature of the trapping centre and to locate its energy level relative to the valence and conduction bands of the YPO4 host. The high-temperature glow peak could unequivocally be assigned to Sm2+ (thus Sm3+ acts as an electron trap). The trap depth of this centre, as derived from the OSL excitation spectra, is in good agreement with the Dorenbos model prediction. The OSL excitation spectra also reveal excited states of Sm2+ well below the conduction band. These excited states produce a broadening of the high-temperature TL glow peak and also cause the activation energy determined by the Hoogenstraten method to underestimate the trap depth. 相似文献
12.
We investigated the admittance spectra of resistive switching Pt/Nb-doped SrTiO3 single-crystal junctions at different resistance states in air and vacuum. The analyses showed that the carrier lifetime at the traps was largely varied depending on the resistance state, indicating the surface potential modification. The ambient dependence suggested that the charges at the trap states were affected by the oxygen adsorption/desorption at the surface. The conductance spectroscopy method clearly revealed the importance of the interface trap states in the resistive switching behavior. 相似文献
13.
Low temperature polarized absorption and magnetic circular dichroism spectra are reported for crystals of CdBr2 doped with varying concentrations of Co2+ in the region near 17 700 cm-1. Sharp zero phonon lines are identified as the trigonal field components of Ug ′(2 T 1g , 2 H) in dilute crystals, and as states arising from ferromagnetically coupled in-plane pairs in the concentrated ones. Measurements of the temperature dependence of the lines, and Zeeman spectra recorded with applied fields up to 50 kG parallel and perpendicular to the crystal c-axis, lead to estimates of the anisotropy of the exchange interaction in the ground state, and to both isotropic and anisotropic exchange in the excited state. The preferred direction of spin alignment in both states is parallel to the c-axis. 相似文献
14.
The kink effect is studied in an AlGaN/GaN high electron mobility transistor by measuring DC performance during fresh, short-term stress and recovery cycle with negligible degradation. Vdg plays an assistant role in detrapping electrons and short-term stress results in no creation of new category traps but an increase in number of active traps. A possible mechanism is proposed that electrical stress supplies traps with the electric field for activation and when device is under test field-assisted hot-electrons result in electrons detrapping from traps, thus deteriorating the kink effect. In addition, experiments show that the impact ionization is at a relatively low level, which is not the dominant mechanism compared with trapping effect. We analyse the complicated link between the kink effect and stress bias through groups of electrical stress states: Vds = 0-state, off-state, on-state (on-state with low voltage, high-power state, high field state). Finlly, a conclusion is drawn that electric field brings about more severe kink effect than hot electrons. With the assistance of electric field, hot electrons tend to be possible to modulate the charges in deep-level trap. 相似文献
15.
S.K. Mishra R.K. Srivastava S.G. Prakash R.S. Yadav A.C. Panday 《Opto-Electronics Review》2010,18(4):467-473
In the present paper, ZnO nanoparticles (NPs) with particle size of 20–50 nm have been synthesized by hydrothermal method.
UV-visible absorption spectra of ZnO nanoparticles show absorption edge at 372 nm, which is blue-shifted as compared to bulk
ZnO. Photoluminescence (PL) and photoconductive device characteristics, including field response, light intensity response,
rise and decay time response, and spectral response have been studied systematically. The photoluminescence spectra of these
ZnO nanoparticles exhibited different emission peaks at 396 nm, 416 nm, 445 nm, 481 nm, and 524 nm. The photoconductivity
spectra of ZnO nanoparticles are studied in the UV-visible spectral region (366–691 nm). In spectral response curve of ZnO
NPs, the wavelength dependence of the photocurrent is very close to the absorption and photoluminescence spectra. The photo
generated current, Ipc = (Itotal - Idark) and dark current Idc varies according to the power law with the applied field IpcαVr and with the intensity of illumination IpcαIL
r, due to the defect related mechanism including both recombination centers and traps. The ZnO NPs is found to have deep trap
of 0.96 eV, very close to green band emission. The photo and dark conductivities of ZnO NPs have been measured using thick
film of powder without any binder. 相似文献
16.
J. Depeyrot P. Tronc E. Umdenstock B. Etienne J.F. Palmier A. Sibille 《Superlattices and Microstructures》1992,12(4)
We report a study of the photoluminescence spectra of GaAs---Ga0.65Al0.35As superlattice under an electric field of about 10 kVcm−1, from 9 K up to 80 K; the ratio
of the intensities of the −1 and 0 peaks of the Wannier-Stark ladder varies with the temperature T. To fit these variations, we assume for both transitions, a trapped exciton density of states with a gaussian distribution of eigenenergies, and a two dimensional density of states for free excitons. We show that above about 50 K there is a thermal equilibrium between direct and crossed free excitons whereas at low temperatures, the equilibrium statistics are not respected: the excitons trap into the direct state rather than to the crossed one. 相似文献
17.
Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact 下载免费PDF全文
Deep levels in Cds/CdTe thin film solar cells have a
potent influence on the electrical property of these devices. As an
essential layer in the solar cell device structure, back contact is
believed to induce some deep defects in the CdTe thin film. With the
help of deep level transient spectroscopy (DLTS), we study the deep
levels in CdS/CdTe thin film solar cells with Te:Cu back contact.
One hole trap and one electron trap are observed. The hole trap H1,
localized at Ev+0.128~eV, originates from the vacancy of Cd
(VCd. The electron trap E1, found at Ec-0.178~eV,
is considered to be correlated with the interstitial Cui=
in CdTe. 相似文献
18.
19.
D.J. Payne G. Paolicelli F. Offi G. Panaccione P. Lacovig G. Beamson A. Fondacaro G. Monaco G. Vanko R.G. Egdell 《Journal of Electron Spectroscopy and Related Phenomena》2009
The core and valence levels of β-PbO2 have been studied using hard X-ray photoemission spectroscopy (hν = 6000 eV and 7700 eV). The Pb 4f core levels display an asymmetric lineshape which may be fitted with components associated with screened and unscreened final states. It is found that intrinsic final state screening is suppressed in the near-surface region. A shift in the O 1s binding energy due to recoil effects is observed under excitation at 7700 eV. It is shown that conduction band states have substantial 6s character and are selectively enhanced in hard X-ray photoemission spectra. However, the maximum amplitude in the Pb 6s partial density of states is found at the bottom of the valence band and the associated photoemission peak shows the most pronounced enhancement in intensity at high photon energy. 相似文献
20.
O. N. Prudnikov A. V. Taichenachev V. I. Yudin E. M. Rasel 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(12):1420-1428
The possible deep laser cooling of 24Mg atoms in a deep optical lattice in the presence of an additional pumping field resonant to the narrow 3s3s1S0 → 3s3p3P1 (λ = 457 nm) optical transition is studied. Two quantum models of the laser cooling of atoms in the optical trap are compared. One is based on the direct numerical solution to the kinetic quantum equation for an atomic density matrix; it considers both optical pumping and quantum recoil effects during interaction between the atoms and field photons. The second, simplified model is based on decomposing the states of the atoms over the levels of vibration in the optical trap and analyzing the evolution of these states. The comparison allows derivation of optical field parameters (pumping field intensity and detuning) that ensure cooling of the atoms to minimal energies. The conditions for fast laser cooling in an optical trap are found. 相似文献