摘要:

Our earlier evidence for a sharp absorption threshold in amorphous Ge is reexamined in view of criticism by Connell and Lewis. Data are presented which show that sharp absorption thresholds can occur and are not artifacts resulting from experimental or calculational errors.

ISSN:0094-243X    

DOI:10.1063/1.2945960

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

An interpretation attributing both sharp and shallow optical absorption edges in amorphous Ge to density of states spectra having shallow overlapping tails is discussed. It is suggested that sharp absorption edges near 0.5 to 0.6 eV are related to the occupation function at the Fermi level for a large density of mid‐gap states rather than to a sharp density of states edge.

ISSN:0094-243X    

DOI:10.1063/1.2945958

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A series of hydrogenated amorphous Ge films was prepared at 25°C. The effect on the electronic properties of incorporating H is found to be similar to that of growth at elevated temperatures or anneal of pure films. From this we conclude that most of the states in the pseudogap are attributable to dangling bonds.

ISSN:0094-243X    

DOI:10.1063/1.2945975

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A.c. photoconductivity (&Dgr;&sgr;) and depolarization current measurements on amorphous films ofGaAswere performed. The following results were obtained: the a.c. photoconductivity is a sum of three components: two photoconductive, with different time constants and a transient thermal component. The depolarization curve as a function of temperature showed two broad maxima. From these results information about the localized levels in a‐GaAswere obtained.

ISSN:0094-243X    

DOI:10.1063/1.2945984

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The porosity P, the free spin density N and the net intrinsic stress &sgr; were measured on evaporated films of amorphous germanium (a‐Ge) subjected to different annealing temperatures Ta. The three quantities N, P and &sgr; decrease with increasing Taand approach zero in the range200 < Ta <300°C. The very similar functional dependence on Taof these quantities suggests that they are associated with the internal void structure observed by several other investigators. This is contrasted with&khgr;a/&khgr;c = 2.5, the ratio of the diamagnetic susceptibilities of amorphous and crystalline germanium, which is independent of Taup to 320°C. Models for the structure of a‐Ge are discussed in light of our data.

ISSN:0094-243X    

DOI:10.1063/1.2945989

出版商:AIP    

年代:1974

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.2945990

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A system has been designed to performin situElectron Spin Resonance measurements on films evaporated under Ultra High Vacuum conditions. Study of amorphous silicon films confirms the existence of a spin density of the order 1020/cm3under conditions where the total possible density of contaminating atoms is one order of magnitude smaller.

ISSN:0094-243X    

DOI:10.1063/1.2945991

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Based on photoemission studies of the surface states of crystalline Si and the effect of oxygen, thereon, the interpretation of electron spin resonance signals in terms of surface states on crystalline or amorphous Ge and Si is questioned. We report attempts to detect filled surface states lying in the band gap directly in photoemission studies of amorphous Ge and Si. No clear evidence for such states has been found to date. The effect of atmospheric exposure on amorphous and crystalline samples has also been studied using reflection measurements. Atmospheric exposure is found to produce much stronger changes in the amorphous films than the crystalline films indicating that the oxide layer is much less protective on these particular amorphous films than on the crystalline films.

ISSN:0094-243X    

DOI:10.1063/1.2945992

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Ultraviolet photoemission spectroscopy (UPS), electron energy loss spectroscopy (ELS) and low energy electron diffraction (LEED) have been combined to study surface states on several silicon (111) surfaces. Amorphous surfaces are obtained by annealing a vacuum‐cleaved sample to 250–400°C where the ordered LEED pattern becomes diffuse or by argon‐ion bombardment. Surface states due to dangling bonds are observed by UPS and ELS for both amorphous and crystalline surface phases but energies and intensities differ for each phase.

ISSN:0094-243X    

DOI:10.1063/1.2945993

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Activation energies of the thermally‐activated reordering processes in high‐density, vapour deposited disordered Ge films are derived from an analysis of intensity variations in second derivative energy distribution photo‐emission spectra. The results indicate that films prepared by carefully controlled cooling to 20°C following vapour‐deposition onto heated polished silica substrates at temperatures in the range120°C ≲ Ts ≲ 140°Cundergo a sharp disordered‐crystalline transition at250 ± 20°Cwith an activation energy of1.4 ± 0.4 eVupon subsequent annealing. This behaviour, together with their d.c. conductivity and photo‐emission spectral profile characteristics, provides strong evidence for a unique continuous network ‘glassy’ state containing a minimum of unsaturated bonds.

ISSN:0094-243X    

DOI:10.1063/1.2945994

出版商:AIP    

年代:1974

数据来源: AIP