摘要:

AQ‐switched ruby laser was used to study both reversible and permanent changes in the electrical conductivity of partially compensatedn‐type andp‐type hydrogenated amorphous silicon (a‐Si:H). This method of illumination provides an accelerated test of the magnitude of reversible photoinduced changes (known as the Staebler–Wronski effect) if the laser beam energy is insufficient to produce gross structural alterations in the samples. Compensated films are less susceptible to Staebler–Wronski changes than are single doped films. At energy densities above about 0.2 J cm−2, recrystallization of these thin films occurs, to an extent dependent on the energy. Energies above about 1.2 J cm−2produced no further increases of conductivity. The total increase in conductivity over this energy range was 104–105forp‐type films and 103–104forn‐type films giving similar saturated conductivity values for both series of films. There were also large improvements in photosensitivity.

ISSN:0021-8979    

DOI:10.1063/1.341967

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Thea‐CSiSn alloy produced by rf magnetron sputtering in SiH4, CH4, and Ar atmosphere was studied as a function of the substrate temperature. The composition of the films was determined by elastic recoil detection analysis and by Rutherford backscattering measurements, and the density was then deduced. Results of a study of optical and electrical properties and of the bonding and structure of the films indicate that with the increase of the substrate temperature, the density and the imaginary part of the dielectric constant increases, the optical gap decreases, and the dark conductivity presents a different conduction mechanism depending on the substrate temperature. A correlation between the results obtained from nuclear measurements and IR spectroscopy is presented.

ISSN:0021-8979    

DOI:10.1063/1.341968

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The influence on magnetic field on 1/fnoise in a planar GaAs resistor grown by molecular‐beam epitaxy and without surface effects was investigated experimentally. The experimental results can be explained by the number fluctuation model but not by the mobility fluctuation model. Previously, experimental results indicating number fluctuation type of 1/fnoise were mostly attributed to the surface effects associated with the particular structures used for the experiments. In our device the surface effects were diminished so that the fluctuations of the bulk current could be considered to produce the 1/fnoise.

ISSN:0021-8979    

DOI:10.1063/1.341940

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We report the first explanation of the novel electrical switching in two‐terminal devices based on thin V2O5⋅1.6H2O gel films. The switching is shown to be associated with the existence of a current‐induced channel between the contacts. The data demonstrate that the switching between the ‘‘on’’ and ‘‘off’’ states of the device is driven by the joule heating of a metal‐insulator (MI) transition in the channel material (or filaments in the channel). Resistivity data on the channel exhibit a sharp MI transition atT=334 K which is also the temperature at which the device is observed to stop switching. The signature of the MI transition in the channel is very similar to that observed in VO2(TMI=341 K), suggesting the channel may contain VO2−xconduction paths.

ISSN:0021-8979    

DOI:10.1063/1.341941

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A recently published dynamic balance model which describes gate‐oxide degradation following prolonged charge injection is modified. This modification replaces the average electric field in the oxide with the electric field spatial distribution. It is shown that a very close interchangeable relationship exists between the electric field spatial distribution and the spatial distributions of the trapped charge and generated trapping sites. The validity of the new modified model is confirmed for different oxide thicknesses (130–720 A˚), injection techniques (hot‐electron injection and constant current‐tunneling injection), and gate electrode material (aluminum versus polycrystalline silicon). The most attractive feature of the modified dynamic balance model is its ability to describe the steady‐state occupation level changes for any given electric field following any oxide stress injection. Furthermore, the modified model is used to propose a new breakdown model which is described in a companion paper.

ISSN:0021-8979    

DOI:10.1063/1.341942

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A recently developed self‐consistent model for gate‐oxide degradation due to charge injection, described in a companion paper, is expanded to include electrical ‘‘wear out’’ breakdown. In the present work, gate‐oxide breakdown is defined to occur when the density of generated neutral trapping sites reaches a critical threshold value at the anode. Breakdown experimental results obtained under constant tunneling current are treated and simulated. The new model deals successfully with oxide breakdown dependence on: injection history, gate‐oxide thickness, charge‐injection current density, injection polarity reversal, gate electrode material, and oxide anneal temperatures.

ISSN:0021-8979    

DOI:10.1063/1.342477

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The electrical resistivity and the Hall coefficient of thin polycrystalline MoSi2films were measured as a function of temperature from 4.2 to 300 K. The transverse and longitudinal magnetoresistances have been determined at temperatures between 2 and 50 K at fields up to 10 T. Samples of both the high‐temperature tetragonal MoSi2phase and the low‐temperature hexagonal phase have been prepared. The Hall coefficient of tetragonal MoSi2changes sign with temperature, which means that this compound is a multiband conductor, and thus no reliable value for the carrier concentration can be derived from Hall measurements alone. Magnetoresistance data have therefore been analyzed with a simple two‐band model in order to determine the dominant carrier type in both MoSi2structures. In tetragonal MoSi2, electrons and holes are present in equal concentrations, whereas in hexagonal MoSi2holes are the dominating type of carrier.

ISSN:0021-8979    

DOI:10.1063/1.341918

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A new method to detect energy‐band bending using x‐ray photoemission spectroscopy has been proposed which measures the changes in the binding energy with the change in the detection angle of photoelectrons. This method was applied to crystalline silicon of various doping conditions with a thin surface oxide and after removing it by ion sputtering. The change in the binding energy with the change in the detection angle was observed only in heavily dopedp‐type silicon before sputtering, but not in other silicon specimens studied in this work. All specimens showed an identical binding energy independent of the detection angle after removing surface oxides by sputtering. These results are explained semiquantitatively using a simple band‐bending model.

ISSN:0021-8979    

DOI:10.1063/1.341919

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

Junctions of CuInSe2/CdS have been investigated using an admittance spectroscopy technique to obtain information on electrically active states in CuInSe2. The junctions studied were fabricated using electrodepositedp‐type CuInSe2films. The admittance experiments were carried out over a temperature range from 80 to 300 K with a frequency range from 1 to 100 kHz. In devices fabricated using CuInSe2films with an In/Cu ratio of 1.10, peaks were observed in the conductance‐temperature curves with an activation energy of about 50 meV. Characteristic peaks with an activation energy of about 160 meV were found in the devices fabricated using CuInSe2films with an In/Cu ratio of about 1.25.

ISSN:0021-8979    

DOI:10.1063/1.341920

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An electron channeling study has been done on large grained YBa2Cu3Oxsamples. Selected area channeling patterns (SACP) were used to examine several dozen grains on electropolished surfaces and it was demonstrated that (a) the twin planes observed in polarized optical light microscopy lie parallel to {110} crystal planes, and (b) the long flat sides of high aspect ratio grains are formed by basal planes, and the shorter sides are formed by either (010), (100), or {110} planes. A majority of the large grains examined were found to contain subgrains, misaligned by 0.5°–1° and ranging in size from less than 3 to 20 &mgr;m. The origin of the subgrains is not understood.

ISSN:0021-8979    

DOI:10.1063/1.341921

出版商:AIP    

年代:1988

数据来源: AIP