摘要:

dc plasma etching experiments were carried out on polycrystalline Si wafers using CF4and CF4/O2mixtures as etchants. The etchants were injected into a slow stream of Ar while a continuous discharge was maintained. The resulting transients of intermediate and product species were determined mass spectrometrically; some of these were found to depend very much on the oxygen concentration, even though hysteresis effects which complicated earlier results were not noticed in this study.The results do not support existing simplified models, but yield some detailed information concerning the etching mechanism. The etch rates increase when small amounts of oxygen are added to the CF4, probably due to an increase in the atomic fluorine concentrations, while at larger oxygen concentrations they decrease, in part because the fragmentation of the etchant gas CF4is then suppressed. CF2radicals are found to be present in the plasma in appreciable concentrations; presumably, this species is directly involved in the formation of SiF4at the surface.

ISSN:0021-8979    

DOI:10.1063/1.335385

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Ionic conductivity &sgr; and mobility &mgr; in the amorphous network polymers from poly(propylene oxide) (PPO) containing lithium perchlorate (LiClO4) at the concentration of [LiClO4]/[PO unit]=0.042 and 0.076 were investigated by means of complex impedance and time‐of‐flight methods. The &sgr; values of the PPO–LiClO4complexes reached 10−5S cm−1at 70 °C. The temperature dependence of &sgr; deviated from a single Arrhenius behavior above a critical temperature (−1 °C and 11 °C) which approximately corresponded to the glass transition temperatureTg. The &mgr; values were relatively high and changed from 10−6to 10−5cm2 V−1 s−1in the temperature range of 40–100 °C. The Nernst–Einstein equation correlated &mgr; with the ionic diffusion coefficientD. The Williams–Landel–Ferry equation withC1&bartil;5 andC2&bartil;30–50 held with a temperature dependence ofDin the order of 10−8–10−7cm2 s−1. The change in the number of ionic carriersnwith temperature obeyed the Arrhenius equation with the activation energy of 0.26 and 0.34 eV. The degree of dissociation for LiClO4in the PPO networks was 1–6%, and the dissociation was facilitated in the low LiClO4concentration complex. The temperature dependence of &sgr; aboveTgwas interpreted quantitatively in terms ofnand &mgr;.

ISSN:0021-8979    

DOI:10.1063/1.335386

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Oxidation of III‐V compound semiconductor (110) cleaved surfaces under light irradiation is studied. The light irradiation enhanced the reaction rate of oxidation but the relationship between oxide growth and oxidation time under logarithmic law scarcely changed within this experimental range. The oxidation trend observed under light irradiation is similar to that of thermal oxidation for GaP, GaAs, InP, InAs, InGaAs, and InGaAsP. Semiconductors having As as the V element tend to be easily oxidized, while those of the above mentioned six kinds of materials having Ga as the III element are quickly oxidized in their initial stage. Ternary and quaternary compound semiconductors have less tendency to be oxidized compared to their constituent binary materials. off

ISSN:0021-8979    

DOI:10.1063/1.335375

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The time dependence of optical density during a coloration and bleaching sequence has been investigated in the isotropic phase for several liquid‐crystalline materials doped with a small amount of tetra‐n‐alkyl‐ammonium iodide. As a result, a rate equation fitting experimental results obtained for low current densities has been derived:dOD/dt=&agr;J−&kgr;(OD+OD0), whereODis the change in optical density of colored cells after the application of dc current,Jis the applied current density, &agr; is a coefficient related to the coloration rate, &kgr; is a coefficient governing the bleaching rate, andOD0is a constant for a given cell. Furthermore, the dependence of these coefficients upon electrolyte concentration, cell thickness, and cell temperature has been studied. The value of &agr; is almost independent of device parameters, while &kgr; is dependent upon the latter two parameters.

ISSN:0021-8979    

DOI:10.1063/1.335376

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown that the performance of photoelectrochemical cells based on the lamellar material InSe can be considerably improved by means of a selective (photo)electrochemical etching. Whereas the cleavage Van de Waals plane (⊥ tocaxis) shows little improvement, the photcurrent in the ∥ face (parallel to thecaxis) is doubled (30 mA cm−2under AM1 illumination). Forn‐type InSe a reverse bias (+1.5 V versus standard calomel electrode SCE) was employed during the photoetching,p‐InSe electrodes were electrochemically etched by applying a forward bias (+1.5 V). In both cases, surface holes carry out the selective corrosion of the semiconductor surface which is another manifestation for the asymmetry played by holes and electrons on semiconductor surfaces. It is hoped that this finding will pave the way for the construction of high‐efficiency solar cells based on a thin film made of lamellar materials.

ISSN:0021-8979    

DOI:10.1063/1.335377

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The electroencephalogram and magnetoencephalogram maps measured on the head can be used to estimate the location, orientation, and amplitude of electrical sources in the brain. It is known that differences in the electrical conductivities of the various tissues in the head can affect these maps and estimates, e.g., the low conductivity of the skull ‘‘smears’’ electroencephalogram maps and makes sources appear deeper in the head than they actually are. Since fissures in the brain are filled with cerebrospinal fluid, which is several times more conductive than the brain tissue in which the sources are located, and since fissures are close to many of the sources, they may have significant effects on the maps and estimates of source parameters. However, little or no information is available about these effects. This study uses a spherically‐shaped computer model of the head which contains fissures to determine these effects. It is found that even a fissure as large as the interhemispheric fissure has a maximum effect on location estimates of 0.75 cm and a maximum effect on orientation estimates of 15°. The maximum effect of this fissure on amplitude estimates is 28% with the estimates being larger than the actual source for sources perpendicular to a fissure and smaller for sources parallel. In general, there are no significant differences in the effects of the fissures on estimates using electroencephalogram and magnetoencephalogram maps. The fissures cause a radial source in the spherically‐shaped head model to produce only a small magnetic field with a map like that of a source perpendicular to the fissure; a radial source in a sphere with no fissures would produce no magnetic field. Since most fissures in the brain are smaller than the ones in this head model, it is concluded that actual fissures in the brain have little effect on electroencephalogram and magnetoencephalogram maps and source estimates using these maps.

ISSN:0021-8979    

DOI:10.1063/1.335378

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A semiempirical analytic central potential model is used to calculate optical oscillator strengths, generalized oscillator strengths, and integrated cross sections up to 5 keV for electrons colliding with sodium atoms. The excitations 3s‐npare discussed, and the results for 3s‐3pare compared to experiment.

ISSN:0021-8979    

DOI:10.1063/1.335379

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Co‐Al2O3composites were prepared by dual electron beam evaporation. When the volume fraction of cobalt is lower than 0.07, the metal is almost completely dispersed as ions in the amorphous oxide matrix. Due to the local ordering of amorphous aluminum oxide, absorption bands caused by crystal field effects are seen in the visible wavelength range. The features of the spectra are consistent with cobalt ions located in tetrahedrally coordinated sites in the oxide. Thus optical absorption measurements can be used to determine whether the metal is present as ions or as particles in various cermet materials.

ISSN:0021-8979    

DOI:10.1063/1.335380

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Cross sections of the patterns fabricated in (100) GaAs by 100‐keV gallium focused ion beam have been studied using a scanning electron microscope (SEM). The probe size of the ion beam is 0.1–0.15 &mgr;m at the current of 100 pA. The etched depth becomes saturated at the high dose region (about 5.0×10−6C/cm) because of the redeposition effect. The pattern profile becomes asymmetric if it is made up of several adjacent lines perpendicular to the beam scanning direction due to the redeposition effect and the increase of sputtering yield for each scan, which is caused by the change of ion beam incident angle. These effects can be eliminated by the use of multiwriting method.

ISSN:0021-8979    

DOI:10.1063/1.335387

出版商:AIP    

年代:1985

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.335512

出版商:AIP    

年代:1985

数据来源: AIP