Temperature Dependent Defect Density Calculated from Activated Conductivity of a-Si:H

1991 ◽  
Vol 219 ◽  
Author(s):  
T. Drusedau ◽  
V. Kirbs ◽  
H. Fiedler
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Defect Density ◽  
State Density ◽  
Level Shift ◽  
Defect State ◽  
Temperature Dependent ◽  
Slow Cooling ◽  
Thermally Activated ◽  
Gap States

ABSTRACTThermally activated conductivity of a—Si:H at a slow cooling rate of 0.3 K/min is connected with temperature dependent changes of the mobility gap states. By means of the Fermi—level shift calculated from these data and a density of states model it is possible to determine this dependence. The results mainly reveal a decrease of the defect state density by about a tenth between 375 K and 400 K.

Defect states in amorphous Ge2Sb2Te5 phase change material

2014 ◽  
Vol 92 (7/8) ◽  
pp. 619-622
Author(s):  
N. Qamhieh ◽  
S.T. Mahmoud ◽  
A.I. Ayesh
Keyword(s):  
Fermi Level ◽  
Energy Gap ◽  
Continuous Distribution ◽  
Dark Conductivity ◽  
Localized States ◽  
Defect States ◽  
Thermally Activated ◽  
Level Shifts ◽  
Gap States ◽  
Change Material

Steady-state photoconductivity measurements in the temperature range 100–300 K on amorphous Ge2Sb2Te5 thin film prepared by dc sputtering are analyzed. The dark conductivity is thermally activated with a single activation energy that allocates the position of the Fermi level approximately in the middle of the energy gap relative to the valance band edge. The temperature dependence of the photoconductivity ensures the presence of a maximum normally observed in chalcogenides with low- and high-temperature slopes, which predict the location of discrete sets of localized states (recombination levels) in the gap. The presence of these defect states close to the valence and conduction band edges leaves the quasi Fermi level shifts in a continuous distribution of gap states at high temperatures, as evidenced from the γ values of the lux–ampere characteristics.

On the interface quality of MIS structures fabricated from Atomic Layer Deposition of HfO2, Ta2O5 and Nb2O5−Ta2O5−Nb2O5 dielectric thin films

2003 ◽  
Vol 786 ◽  
Author(s):  
S. Dueñas ◽  
H. Castán ◽  
H. García ◽  
J. Barbolla ◽  
K. Kukli ◽  
...  
Keyword(s):  
Thin Films ◽  
Defect Density ◽  
Deep Level ◽  
Atomic Layer ◽  
Interface State ◽  
State Density ◽  
Interface Quality ◽  
Transient Spectroscopy ◽  
Gap States ◽  
Mis Structures

ABSTRACTA study of metal-insulator-semiconductor (MIS) structures based on atomic layer deposited HfO2, Ta2O5 and Nb2O5−Ta2O5−Nb2O5 thin films is presented. Our attention was focussed on interface quality and defect density in the dielectric. Interface states as well as defects inside the insulator bulk were measured by using capacitance-voltage (C-V), deep level transient spectroscopy (DLTS) and conductance transient (G-t) techniques. Nb2O5−Ta2O5−Nb2O5 based capacitors exhibit the highest interface state density, whereas the minimum is obtained for HfO2. Conductance transients are not observed in Al/HfO2/SiO2/Si stacks, thus indicating that disordered induced gap states (DIGS) are not present in these structures. We also observed that post-metallization annealing in forming gas diminishes the trap interface density at the expense of increasing DIGS in the Al/HfO2/Si cases.

Deep States in a-Si:H - Changes with Doping and Applied Stress.

1987 ◽  
Vol 95 ◽  
Author(s):  
J. Kočka ◽  
M. Vanéček
Keyword(s):  
Fermi Level ◽  
Charge State ◽  
Applied Stress ◽  
Density Of States ◽  
Driving Force ◽  
External Stress ◽  
Strong Increase ◽  
Level Shift ◽  
Dangling Bond ◽  
Bond Density

AbstractRecent Constant Photocurrent Method (CPM) results and a new model of a-Si:H density of states are briefly reviewed. The small but systematic changes of subgap absorption (α) with the applied external stress have been found. When light-soaking is done under the applied stress the strong increase of α is observed. The μτ (mobility-lifetime) versus α duality is demonstrated. The increase of the dangling bond density, combined with the change of its charge state, is used for the explanation of duality. The light induced creation of dangling bond-impurity intimate pairs is speculated to be the driving force for the Fermi level shift.

Gap States in Hydrogenated Amorphous Silicon—Carbon Alloys

1985 ◽  
Vol 49 ◽  
Author(s):  
P. Fiorini ◽  
F. Evangelisti ◽  
A. Frova
Keyword(s):  
Amorphous Silicon ◽  
Recombination Rate ◽  
Transport Mechanism ◽  
Hydrogenated Amorphous Silicon ◽  
State Density ◽  
Defect State ◽  
Defect States ◽  
Silicon Carbon ◽  
Gap States ◽  
Hydrogenated Amorphous

AbstractTail and defect states in the gap of a-SixCl-x:H alloys have been studied by measurements of spectral photoconductivity. The variation of defect—state density versus x is found to be negligible. By comparison with PDS results the ητ product has been determined and found to be almost independent of photonenergy and to strongly decrease with inclusion of carbon. This effect is attributed to changes in the transport mechanism combined with an increased recombination rate associated with the widening of the gap.

ABSORPTION SPECTROSCOPY OF ELECTRONIC STATES NEAR FERMI LEVEL: TEMPERATURE CHANGES OF SUPERCONDUCTING YBa2Cu3O7−δ FILMS AT Tc

1992 ◽  
Vol 06 (09) ◽  
pp. 1475-1489 ◽  
Author(s):  
I. YA. FUGOL ◽  
V.N. SAMOVAROV ◽  
YU. I. RYBALKO ◽  
V.M. ZHURAVLEV
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Energy Region ◽  
Local Level ◽  
Electronic States ◽  
Superconducting Transition ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
Optical Gap ◽  
Dependent Behaviour

The temperature behavior of the absorption spectra of superconducting YBa 2Cu3O7−δ textured films is measured in a 1.5÷3.0 eV energy region with varying temperatures from 25 to 300 K. The spectra are found to be sensitive to a superconducting transition: the temperature-dependent behaviour of absorption at T>Tc undergoes critical changes under the superconducting transition and for T<Tc the spectrum ceases to depend on temperature. The spectra display an exciton maximum in the optical gap Eg=1.95 eV. The spectrum freezing at T<Tc can be explained assuming that the Fermi level is in temperature resonance with a narrow local level which is responsible for a delta-like singularity in the density of states.

scholarly journals Investigation of single-domain Au silicide nanowires on Si(110) formed for Au coverages in the monolayer regime

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Stephan Appelfeller
Keyword(s):  
Fermi Level ◽  
Surface Structure ◽  
Density Of States ◽  
The Self ◽  
Single Domain ◽  
Photoemission Spectroscopy ◽  
Annealing Temperatures ◽  
Self Organized ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy

AbstractThe self-organized formation of single domain Au silicide nanowires is observed on Si(110). These nanowires are analysed using scanning tunnelling microscopy (STM) and spectroscopy (STS) as well as photoemission spectroscopy (PES). Core-level PES is utilised to confirm the formation of Au silicide and establish its presence as the top most surface structure, i.e., the nanowires. The growth of the Au silicide nanowires and their dimensions are studied by STM. They form for Au coverages of about 1 monolayer and are characterized by widths of about 2 to 3 nm and heights below 1 nm while reaching lengths exceeding 500 nm when choosing appropriate annealing temperatures. Valence band PES and STS indicate a small but finite density of states at the Fermi level typical for compound metals.

scholarly journals Tetragonal–Cubic Phase Transition and Low-Field Dielectric Properties of CH3NH3PbI3 Crystals

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4215
Author(s):  
Roxana E. Patru ◽  
Hamidreza Khassaf ◽  
Iuliana Pasuk ◽  
Mihaela Botea ◽  
Lucian Trupina ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Current Knowledge ◽  
Cubic Phase ◽  
Relaxation Processes ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Low Field ◽  
Conduction Mechanisms ◽  
Temperature Ranges ◽  
Nyquist Plots

The frequency and temperature dependence of dielectric properties of CH3NH3PbI3 (MAPI) crystals have been studied and analyzed in connection with temperature-dependent structural studies. The obtained results bring arguments for the existence of ferroelectricity and aim to complete the current knowledge on the thermally activated conduction mechanisms, in dark equilibrium and in the presence of a small external a.c. electric field. The study correlates the frequency-dispersive dielectric spectra with the conduction mechanisms and their relaxation processes, as well as with the different transport regimes indicated by the Nyquist plots. The different energy barriers revealed by the impedance spectroscopy highlight the dominant transport mechanisms in different frequency and temperature ranges, being associated with the bulk of the grains, their boundaries, and/or the electrodes’ interfaces.

Photosensitive tunneling in superconductivity

1970 ◽  
Vol 48 (5) ◽  
pp. 630-631 ◽  
Author(s):  
V. Radhakrishnan
Keyword(s):  
Fermi Level ◽  
Density Of States ◽  
Tunneling Current ◽  
Theoretical Treatment ◽  
Photoconductive Property

Theoretical treatment of the model proposed by Giaever for his experiment on the photosensitive tunneling in superconductors is examined. New relations are derived which connect the photoconductive property of the barrier and the tunneling current. These relations are helpful to check the model and to determine the density of states for the trapped holes at the hole Fermi level.

Investigations of Tail and Defect States in a-Si0.6Ge0.4:H Alloys by PDS and ESR - Implications for the Interaction of Weak and Dangling Bonds

1995 ◽  
Vol 377 ◽  
Author(s):  
Tilo P. Drüsedau ◽  
Andreas N. Panckow ◽  
Bernd Schröder
Keyword(s):  
Silicon Germanium ◽  
Defect Density ◽  
State Density ◽  
Model Parameters ◽  
Defect States ◽  
Conversion Model ◽  
Order Of Magnitude ◽  
Underlying Mechanisms ◽  
Amorphous Silicon Germanium ◽  
Excess Absorption

ABSTRACTInvestigations on the gap state density were performed on a variety of samples of hydrogenated amorphous silicon germanium alloys (Ge fraction around 40 at%) containing different amounts of hydrogen. From subgap absorption measurements the values of the “integrated excess absorption” and the “defect absorption” were determined. Using a calibration constant, which is well established for the determination of the defect density from the integrated excess absorption of a-Si:H and a-Ge:H, it was found that the defect density is underestimated by nearly one order of magnitude. The underlying mechanisms for this discrepancy are discussed. The calibration constants for the present alloys are determined to 8.3×1016 eV−1 cnr2 and 1.7×1016 cm−2 for the excess and defect absorption, respectively. The defect density of the films was found to depend on the Urbach energy according to the law derived from Stutzmann's dangling bond - weak bond conversion model for a-Si:H. However, the model parameters - the density of states at the onset of the exponential tails N*=27×1020 eV−1 cm−3 and the position of the demarcation energy Edb-E*=0.1 eV are considerably smaller than in a-Si:H.

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