Time-of-Flight Measurement on a-Ge:H and a-SiGe:H Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
E.Z. Liu ◽  
D. Pang ◽  
W. Paul ◽  
J.H. Chen
Keyword(s):  
Room Temperature ◽  
Transport Model ◽  
Drift Mobility ◽  
Band Tail ◽  
High Quality ◽  
Hopping Transport ◽  
Flight Measurement ◽  
Order Of Magnitude ◽  
Temperature Ranges ◽  
Electron Drift Mobility

ABSTRACTWe report TOF measurements on high quality intrinsic a-Ge:H and a-SiGe:H films of E04=1–4.eV in temperature ranges of 200 to 280 and 230 to 300K, respectively. Complete charge collection is achieved in all measurements. For a-Ge:H films, the (μτ)e product obtained from the Hecht plot is (5±3)×10-8 cm2/V above 240K and decreases at lower temperatures. The electron transit signal is dispersive at all temperatures. The a obtained from ttV-1/αis 0.23 at 200K and approaches 1.0 at 260K. The electron drift mobility μd shows activated behavior, with an energy of 0.37±0.05eV, and has an extrapolated room temperature value of 0.03 cm2/Vs. Compared to a-Ge:H, μd of a-SiGe:H alloy samples is lower by one order of magnitude but has a similar activation energy. These results are consistent with a band tail hopping transport model.

Time-of-Flight Measurements in a-Si:H Between Room Temperature and 130° C°

1987 ◽  
Vol 95 ◽  
Author(s):  
D. S. Shen ◽  
S. Aljishi ◽  
Z E. Smith ◽  
J. P. Conde ◽  
V. Chu ◽  
...  
Keyword(s):  
Computer Simulation ◽  
Room Temperature ◽  
Time Of Flight ◽  
High Sensitivity ◽  
Drift Mobility ◽  
Hole Transport ◽  
Dispersive Transport ◽  
Band Tail ◽  
Flight Measurements

AbstractThe drift mobility μd and the mobility-lifetime product μτ in undoped a-Si:H have been studied up to 130°C. The electron μde is temperature-activated with Eae = 0.13 to 0.16 eV. The electron (μτ)e increases with temperature T. For hole transport, we observe the transition from dispersive to non-dispersive transport with increasing T. The hole μdh is ∼ 1/100 of μde, and is activated with Eah = 0.34 to 0.48eV. The hole (μτ)h does not change much with T. A computer simulation demonstrates the high sensitivity of μd to the band tail width.

Laufzeitmessungen in Fluoren-Einkristallen / Transit Time Measurements in Fluorene Single Crystals

1977 ◽  
Vol 32 (6) ◽  
pp. 580-587
Author(s):  
H. Eckhardt
Keyword(s):  
Single Crystals ◽  
Transit Time ◽  
Low Temperatures ◽  
Pulse Shape ◽  
Room Temperature ◽  
Trap Depth ◽  
Drift Mobility ◽  
Temperature Ranges ◽  
Increasing Temperature ◽  
Shallow Traps

Abstract The hole drift mobility in single crystals of fluorene was determined by transit time measurements. At room temperature the mobility along the c-axis is (0,82 ± 0,14) cm2/Vs and in the abplane (0,72 ± 0,1) cm2/Vs. In the temperature ranges 200K<T<300K and 165K<T<300K μc and μab have been found to be ~T-1,5 and ~T-1,0, respectively. In both cases the mobility reaches a constant value for low temperatures (100 K). In the range 300 K<T<345 K μ decreases very strongly with increasing temperature {μ~T-5). Traps, especially deep and shallow surface traps, influence the pulse heighth and the pulse shape. From the change of the pulse shape with temperature a trap depth EH = 0,4 eV for shallow traps is determined.

A Novel Preparation Technique Termed “Chemical Annealing” to make a Rigid and Stable Si-Network

1991 ◽  
Vol 219 ◽  
Author(s):  
Hajime Shirai ◽  
Jun-Ichi Hanna ◽  
Isamu Shimizu
Keyword(s):  
Atomic Hydrogen ◽  
Room Temperature ◽  
Drift Mobility ◽  
Preparation Technique ◽  
Dispersive Transport ◽  
Optical Gap ◽  
Chemical Annealing ◽  
Flight Measurement ◽  
The Stability

ABSTRACTA novel preparation technique termed “Chemical Annealing (CA)” was developed with aim of making a stable and rigid structure of Si-network. The a-Si:H films were made by the alternate deposition of several tens angstrom thick a-Si:H and the treatment with atomic hydrogen or excited novel gases such as Ar* and He*. Hydrogen contents (CH) and optical gap (Eg) in the film prepared by this tecnique were able to reduced by CH of 1.5at%, and Eg of 1.5eV, respectively at substrate temperature:300C. All of them exhibited high photoconductivities in the level of 10-5 10-4 S/cm under illumination of 100mW/cm2. In the films with CH of 3at% or less, in particular, marked improvement was confirmed in the stability after light soaking. In addition, the time-of-flight measurement revealed a non-dispersive transport and a significant enhancement in the drift mobility of holes up to 0.2cmm2/Vs at room temperature in the film with CH : 5at% and Eg:1.65eV prepared at 300C. Advantages of the CA process are summarized together with the discussion of role of atomic hydrogen, excited novel gases such as Ar* and He* in the growing surface.

Control of the Electron and Hole Drift mobilities in Plasma Deposited a-Si:H

1994 ◽  
Vol 336 ◽  
Author(s):  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Room Temperature ◽  
Film Growth ◽  
Drift Mobility ◽  
Growth Surface ◽  
Band Tail ◽  
Capacitively Coupled ◽  
Deposition Parameters ◽  
Optimum Energy ◽  
Temperature Dependences ◽  
Stimulation Of

ABSTRACTThe ‘time-of-flight’ technique measured electron and hole drift mobilities are shown to be independent of deposition parameters in capacitively coupled, diode type RF-PECVD a-Si:H. However, the carrier mobilities can be varied by orders of magnitude by changing the bias applied to the mesh type controlling electrode in a triode type reactor. The room temperature hole drift mobility increases to 10−1cm2/Vs when an appropriate bias is applied to the mesh providing optimum energy ion stimulation of the film growth surface during deposition. Analysis of the field and temperature dependences of the drift mobilities shows that in the best specimens the conduction (valence) band tail density of states are approximately exponential with a reciprocal slope of lOMeV (25MeV).

μτ Products of 10−6 cm2V−1 Deduced from Eleverse-Bias Dependence of Carrier-Collection Measurements in High Drift Mobility a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
Gautam Ganguly ◽  
Akihisa Matsuda
Keyword(s):  
Valence Band ◽  
Room Temperature ◽  
Reverse Bias ◽  
Film Growth ◽  
Schottky Diodes ◽  
Drift Mobility ◽  
Band Tail ◽  
Measured Voltage ◽  
Voltage Dependent ◽  
Carrier Collection

ABSTRACTThe room temperature hole drift mobility measured by the ‘time-of-flight’ technique can be increased to 0.5 cm2/Vs with a valence band tail width of 25meV by optimizing the ion impingement energy during film growth using a triode configured PECVD reactor. The reverse bias dependence of the carrier collection in Au Schottky diodes formed on these specimens show significantly improved carrier collection which can be approximately quantified using the C-V measured voltage dependent depletion widths to yield μτ≈10−6cm2V−1.

scholarly journals Electronic nematicity in Sr2RuO4

2020 ◽  
Vol 117 (20) ◽  
pp. 10654-10659 ◽  
Author(s):  
Jie Wu ◽  
Hari P. Nair ◽  
Anthony T. Bollinger ◽  
Xi He ◽  
Ian Robinson ◽  
...  
Keyword(s):  
Thin Films ◽  
Room Temperature ◽  
Lattice Distortion ◽  
Sensitive Indicator ◽  
Crystallographic Axis ◽  
Unconventional Superconductor ◽  
High Quality ◽  
Large Lattice ◽  
Order Of Magnitude ◽  
Electronic Nematicity

We have measured the angle-resolved transverse resistivity (ARTR), a sensitive indicator of electronic anisotropy, in high-quality thin films of the unconventional superconductor Sr2RuO4 grown on various substrates. The ARTR signal, heralding the electronic nematicity or a large nematic susceptibility, is present and substantial already at room temperature and grows by an order of magnitude upon cooling down to 4 K. In Sr2RuO4 films deposited on tetragonal substrates the highest-conductivity direction does not coincide with any crystallographic axis. In films deposited on orthorhombic substrates it tends to align with the shorter axis; however, the magnitude of the anisotropy stays the same despite the large lattice distortion. These are strong indications of actual or incipient electronic nematicity in Sr2RuO4.

Interstitial Trapped Hydrogen Molecules in Pecvdamorphous Silicon

1999 ◽  
Vol 557 ◽  
Author(s):  
R. Borzi ◽  
F. Mascarenhas ◽  
P. A. Fedders ◽  
D. J. Leopold ◽  
R. E. Norberg ◽  
...  
Keyword(s):  
Activation Energy ◽  
Molecular Hydrogen ◽  
Pulse Sequences ◽  
High Quality ◽  
Hopping Transport ◽  
Hydrogen Molecules ◽  
Order Of Magnitude ◽  
Si Films ◽  
Molecular Components ◽  
Radiofrequency Pulse

AbstractNew NMR measurements show that interstitial T site-trapped molecular hydrogen can amount to more than one third of the contained hydrogen in high quality PECVD amorphous silicon. Microvoid-contained dense molecular hydrogen is negligible in these good films. Experiments on a sequence of hydrogenated and/or deuterated a-Si films have characterized individually-trapped molecular HD and D2 in films deposited from SiD4, and from SiH4+D2. The T site-trapped molecular hydrogen fraction observed here is larger than previously reported because of recent efforts to measure very slowly relaxing molecular components and the employment of radiofrequency pulse sequences to detect ortho-D2 with nuclear spin I=2. The population of interstitially trapped molecular hydrogen increases with increasing photovoltaic quality over a range of an order of magnitude in photoresponse product ημτ. Above 200 K, hopping transport of molecular hydrogen among the amorphous equivalent of interstitial T sites occurs with an activation energy near 50 meV.

Luminescence Properties of Europium-Doped Yttrium Oxides Derived from Their Dodecylsulfate-Templated Mesostructure and Nanotube Forms

2003 ◽  
Vol 775 ◽  
Author(s):  
Tsuyoshi Kijima ◽  
Kenichi Iwanaga ◽  
Tomomi Hamasuna ◽  
Shinji Mohri ◽  
Mitsunori Yada ◽  
...  
Keyword(s):  
Room Temperature ◽  
Broad Band ◽  
Concentration Quenching ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Bulk Materials ◽  
Main Band ◽  
Homogeneous Precipitation Method ◽  
Order Of Magnitude ◽  
Weak Luminescence

AbstractEuropium-doped hexagonal-mesostructured and nanotubular yttrium oxides templated by dodecylsulfate species as well as surfactant free bulk oxides were synthesized by the homogeneous precipitation method. All the as grown nanostructured or bulk materials with amorphous or poorly crystalline frameworks showed weak luminescence bands at room temperature. On calcination at 1000°C these materials were converted into highly crystalline yttrium oxides, resulting in a total increase in intensity of all the bands by one order of magnitude. In the hexagonal-mesostructured system, the main band due to the 5D0-7F2 transition for the calcined phases showed a sharp but asymmetrical multiplet splitting indicating multiple Eu sites. Concentration quenching was found at a Eu content of 3 mol% or above for these phases. In contrast, the main emission for the calcined solids in the nanotubular system occurred as poorly resolved broad band and the intensity of the main band at higher Eu content was significantly enhanced compared with those for the other two systems.

Temperature Dependence of the Self-Assembled Styrene Based Random Ionomers in Aqueous Solution

2003 ◽  
Vol 775 ◽  
Author(s):  
Sung-Hwa Oh ◽  
Ju-Myung Song ◽  
Joon-Seop Kim ◽  
Hyang-Rim Oh ◽  
Jeong-A Yu
Keyword(s):  
Partition Coefficients ◽  
Room Temperature ◽  
Aqueous Media ◽  
The Self ◽  
Spectroscopic Methods ◽  
Ion Content ◽  
Repeat Units ◽  
Notable Effect ◽  
Order Of Magnitude ◽  
Experimental Errors

AbstractSolution behaviors of poly(styrene-co-sodium methacrylate) were studied by fluorescence spectroscopic methods using pyrene as a probe. The mol% of methacrylate was in the range 3.6–9.4. Water and N,N-dimethylforamide(DMF) mixture was used as a solvent (DMF/water = 0.2 mol %). The critical micelle (or aggregation) concentrations of ionomers and the partition coefficients of pyrene were obtained the temperature range 10–80°C. At room temperature, the values of CMCs (or CACs) were in the range 4.7 ×10-6 5.3 ×10-6 g/mL and we could not find any notable effect of the content of ionic repeat units within the experimental errors. Unlike CMCs, as the ion content increased, partitioning of pyrene between the hydrophobic aggregates and an aqueous media decreased from 1.5 ×105 to 9.4 ×104. As the temperature increased from 10 to 80 °C, the values of CMCs increased less than one order of magnitude. While, the partition coefficients of pyrene decreased one order of magnitude and the effect of the ion content became negligible.

scholarly journals Urban Air Quality Modeling Using Low-Cost Sensor Network and Data Assimilation in the Aburrá Valley, Colombia

Atmosphere ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 91
Author(s):  
Santiago Lopez-Restrepo ◽  
Andres Yarce ◽  
Nicolás Pinel ◽  
O.L. Quintero ◽  
Arjo Segers ◽  
...  
Keyword(s):  
Air Quality ◽  
Data Assimilation ◽  
Transport Model ◽  
Cost Model ◽  
Low Cost ◽  
Model Performance ◽  
Monitoring Network ◽  
Correlation Factor ◽  
Chemical Transport Model ◽  
High Quality

The use of low air quality networks has been increasing in recent years to study urban pollution dynamics. Here we show the evaluation of the operational Aburrá Valley’s low-cost network against the official monitoring network. The results show that the PM2.5 low-cost measurements are very close to those observed by the official network. Additionally, the low-cost allows a higher spatial representation of the concentrations across the valley. We integrate low-cost observations with the chemical transport model Long Term Ozone Simulation-European Operational Smog (LOTOS-EUROS) using data assimilation. Two different configurations of the low-cost network were assimilated: using the whole low-cost network (255 sensors), and a high-quality selection using just the sensors with a correlation factor greater than 0.8 with respect to the official network (115 sensors). The official stations were also assimilated to compare the more dense low-cost network’s impact on the model performance. Both simulations assimilating the low-cost model outperform the model without assimilation and assimilating the official network. The capability to issue warnings for pollution events is also improved by assimilating the low-cost network with respect to the other simulations. Finally, the simulation using the high-quality configuration has lower error values than using the complete low-cost network, showing that it is essential to consider the quality and location and not just the total number of sensors. Our results suggest that with the current advance in low-cost sensors, it is possible to improve model performance with low-cost network data assimilation.

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