Electron Transport and Conduction-Band-Tail States in a-Si:H Deposited with a Remote Hydrogen Plasma

1993 ◽  
Vol 297 ◽  
Author(s):  
C.E. Nebel ◽  
R.A. Street ◽  
N.M. Johnson ◽  
J. Walker
Keyword(s):  
Electron Transport ◽  
Conduction Band ◽  
Defect Density ◽  
Plasma Deposition ◽  
Hydrogen Plasma ◽  
Band Tail ◽  
Mobility Edge ◽  
Characteristic Energy ◽  
Tail State ◽  
Electron Transport Properties

Electron transport properties of a-Si:H prepared in a remote hydrogen plasma deposition reactor (RHPD) at TD = 400°C were investigated in the temperature regime 110 K ≤ T ≤ 300 K by time-of-flight and post-transit spectroscopy experiments. Based on these data the conduction-band-tail state distribution was calculated. In the energy range 85 meV ≤ Ec- E ≤ 350 meV below the mobility edge Ec the tail is well described by an exponential distribution with a characteristic energy of ≃ 21 meV. Deeper in the mobility gap (Ec-E > 350 meV) the tail smoothly passes over into the defect density which is approximately six orders of magnitude smaller than at the mobility edge. Comparisons with data deduced on conventionally prepared a-Si:H (RF-, DC-glow discharge) at TD = 230 °C show that electron transport and the conduction band tail of the RHPD material are comparable.

Distribution of Gap States in Highly Photosensitive a-SiC:H

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Akita ◽  
Y. Nakayama ◽  
M. Yamano ◽  
T. Kawamura
Keyword(s):  
Electron Transport ◽  
Transport Properties ◽  
Conduction Band ◽  
Time Of Flight ◽  
Band Tail ◽  
Carbon Incorporation ◽  
Electron Transport Properties ◽  
Transient Spectroscopy ◽  
Gap States

ABSTRACTThe effect of carbon incorporation into a-Si:H has been investigated in terms of gap states. The shallow and deep states are measured by a combination of two methods of the time-of-flight and the depletion discharge transient spectroscopy. The results show that the carbon incorporation of 10Z into a-Si:H leads to a slight increase in the conduction-band tail states and an extention of the deep states distribution. However, the increase in the shallow states affects little change in the electron transport properties. The origin of the deep states is also discussed.

Band Tails and Thermal Disorder in Doped and Undoped Hydrogenated Amorphous Silicon and Silicon-Germanium Alloys

1990 ◽  
Vol 192 ◽  
Author(s):  
Samer Aljishi ◽  
J. David Cohen ◽  
Shu Jin ◽  
Lothar Ley
Keyword(s):  
Valence Band ◽  
Conduction Band ◽  
Photoelectron Spectroscopy ◽  
Silicon Germanium ◽  
Total Yield ◽  
Structural Disorder ◽  
Band Tail ◽  
Characteristic Energy ◽  
Densities Of States ◽  
Thermal Disorder

ABSTRACTThe energy distribution and temperature dependence of the conduction and valence band tail density of states in a-Si:H and a-Si,Ge:H alloys is determined via total yield photoelectron spectroscopy. All films are observed to possess purely exponential conduction and valence band tail densities of states; however, the characteristic energy of the conduction band tail increases much more rapidly with temperature in the range of 300K to 550K than that of the valence band tail. This indicates that over that temperature range the conduction band tail is considerably more susceptible to thermal disorder than to structural disorder whereas the reverse holds for the valence band tail.

Electron and Hole Transport in a-SiH at High Field and Low Temperature

1992 ◽  
Vol 258 ◽  
Author(s):  
C. E. Nebel ◽  
R. A. Street
Keyword(s):  
Electron Transport ◽  
Low Temperature ◽  
Field Effect ◽  
High Field ◽  
Hole Transport ◽  
Space Charge Limited Current ◽  
Band Tail ◽  
Tail State ◽  
Current Decay ◽  
Enhanced Conductivity

ABSTRACTLow temperature, high field properties of electron and hole transport are investigated by time-of-flight (TOF), steady-state and transient space charge limited current (SCLC) experiments on intrinsic a-Si:H. Charge collection and TOF experiments performed at T= 80 K reveal hole μτ-products of = 8 × 10-10 cm2/V and hole mobilities μ ≤ 9×10-3 cm2/Vs. The field effect on hole thermalization is demonstrated by evaluation of the post transit current decay. SCLC experiments on p+ -i-n+ (electron transport) and p + -i-n+ (hole transport) configurations are introduced and interpreted in terms of field enhanced conductivity and mobility. The experiments demonstrate the overwhelming field effect on carrier hopping in the band tail regions of a-Si:H. Considerably higher fields have to be applied in the case of hole transport than electron transport to achieve comparable conductivities; this is discussed on the basis of the different tail state distributions and localization lengths.

Hopping of Electrons in Hybrid Band Tails of a-Si1-xGex:H

1990 ◽  
Vol 192 ◽  
Author(s):  
C. E. Nebel ◽  
H. C. Weller ◽  
G.H. Bauer
Keyword(s):  
Conduction Band ◽  
Alloy Composition ◽  
Time Of Flight ◽  
State Density ◽  
Mobility Edge ◽  
Medium Temperature ◽  
Tail State ◽  
Current Decay ◽  
Thermally Activated ◽  
Multiple Trapping

ABSTRACTThe thermalization of electrons in the medium temperature range (120K ≤ T ≤ 200K) is investigated by time-of-flight experiments on a-SiGe:H mim structures. The evaluation of the pre-transit current decay reveals a dual slope characteristic which reflects an initial hopping down (I ∼ t−1) followed by a thermally activated (I ∼ t−p 0 < p < 1) process. The transition time from hopping down to multiple trapping sensitively depends on temperature and alloy composition. The experimentally deduced features can be explained by the increased tail state density at the conduction band mobility edge of a-SiGe:H samples compared to a-Si:H.

An Experimental Evaluation of Modulated Photocurrent Spectroscopy as A Density of States Probe

1999 ◽  
Vol 557 ◽  
Author(s):  
S. Reynolds ◽  
C. Main ◽  
D.P. Webb ◽  
M.J. Rose
Keyword(s):  
Thermal Activation ◽  
Optical Excitation ◽  
Band Tail ◽  
Characteristic Energy ◽  
Tail State ◽  
Transient Photocurrent ◽  
Photocurrent Spectroscopy ◽  
A Value ◽  
Quasi Fermi Level ◽  
Absolute Density

AbstractModulated and Fourier-transformed transient photocurrent (MPC and TPC-FT) spectroscopies have been evaluated through a study of the density and capture properties of localised states in as-prepared and light-soaked PECVD a-Si:H samples over a range of temperatures and optical excitations. Both techniques return a conduction band tail state characteristic energy of approximately 22 meV. However, defect state spectra differ in detail and are strongly influenced by dc optical excitation. A feature correlating with the quasi-Fermi level position is observed, but the capture coefficient implied (of order 10-6 cm3 s-1) is some two orders greater than that calculated from thermal activation of emission frequencies. Such a value would suggest an implausibly low absolute density of defects. Possible explanations are briefly discussed and additional investigations proposed.

Magnetic and electron transport properties of Co2Si nanomagnets

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Balamurugan Balasubramanian ◽  
Tom A. George ◽  
Priyanka Manchanda ◽  
Rabindra Pahari ◽  
Ahsan Ullah ◽  
...  
Keyword(s):  
Electron Transport ◽  
Transport Properties ◽  
Electron Transport Properties

Printable Single-Unit-Cell-Thick Transparent Zinc-Doped Indium Oxides with Efficient Electron Transport Properties

ACS Nano ◽  
2021 ◽  
Author(s):  
Azmira Jannat ◽  
Nitu Syed ◽  
Kai Xu ◽  
Md. Ataur Rahman ◽  
Md. Mehdi Masud Talukder ◽  
...  
Keyword(s):  
Electron Transport ◽  
Transport Properties ◽  
Single Unit ◽  
Unit Cell ◽  
Electron Transport Properties ◽  
Indium Oxides

In-situ photoconductivity measurement of imidazole in optical fiber break-junctions

2021 ◽  
Author(s):  
Zhikai Zhao ◽  
Chenyang Guo ◽  
Lifa Ni ◽  
Xueyan Zhao ◽  
Surong Zhang ◽  
...  
Keyword(s):  
Electron Transport ◽  
Optical Fiber ◽  
Transport Properties ◽  
Molecular Junctions ◽  
Break Junction ◽  
Break Junctions ◽  
Fiber Break ◽  
Electron Transport Properties ◽  
Photoconductivity Measurement

We develop a method based on the mechanically controllable break junction technique to investigate the electron transport properties of single molecular junctions upon fiber waveguided light. In our strategy, a...

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