摘要:

Structural changes in amorphous Ge, GeSe2and GeSeTe films by illumination and annealing have been investigated by using a transimission electron microscope. As‐deposited amorphous Ge films have a large number of voids which are observed in micrographs as bright, or density‐deficient, regions. Annealing at 300 °C or illumination makes the film homogeneous, while by annealing at 450 °C the structure changes to fine granular one. Structure of as‐deposited GeSe2films, in which grain‐like morphology is observed, becomes facet‐like by illumination and homogeneous by annealing at 300 °C. There exists photo‐induced instability in GeSeTe films: the crystallization temperature is lowered by illumination. These results suggest that lone pair states of Se and Te atoms in their Ge alloys are excited by illumination to cause structural change.

ISSN:0094-243X    

DOI:10.1063/1.30751

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We have constructed and measured by hand a 539‐atom model for the structure of amorphous selenium. The model consists of densely packed but convoluted chains of covalently bonded 2‐fold coordinated atoms. The model was computer relaxed under potentials that represent bending and stretching of covalent bonds and the van der Waals interactions between the chains. The density and the first four peaks in the radial distribution function are compared with some success with experimental results on amorphous Se and new insight into its structure is obtained.

ISSN:0094-243X    

DOI:10.1063/1.30752

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

An inhomogeneous structure such as the one known for evaporated amorphous Ge films has also been found in evaporated amorphous Si and sputtered CoGd films. This structure is characterized by a coherent supernetwork (SN) of low density material filling the channels between the rodlike high density regions. The properties and implications of the SN and the possible mechanisms for its development are discussed.

ISSN:0094-243X    

DOI:10.1063/1.30753

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The use of optical probes for extracting information on the structure of disordered solids is discussed with particular emphasis on Raman and Depolarization spectroscopic techniques. We show that long wavelength probes can provide details of subtle structural differences and are thus complementary to the more conventional short wavelength x ray probe. Examples of the diversity of structural information which can be deduced with an optical probe are cited.

ISSN:0094-243X    

DOI:10.1063/1.30755

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The compositional dependence of the Raman spectra of GexS1−xglasses has been investigated in comparison with the Raman spectra of crystalline GeS2and GeS. The results reveal that the appearance of minority configurations, (−S2−)nand GeS, is stoichiometry‐sensitive. Discussion is given on the basis of the phase diagram. The stoichiometry‐sensitive properties of ESR, luminescence and internal friction corresponds to the structural characteristics.

ISSN:0094-243X    

DOI:10.1063/1.30756

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

By comparison of Raman and infrared spectra we show that longitudinal vibrational modes account for several of the peaks observed in the first order Raman spectrum of vitreous SiO2. Upon identification of the longitudinal modes, and one defect mode, transverse modes are revealed whose number and position are in good agreement with the predictions of a simple molecular model representing local forces in the perfect network. These results suggest that Coulomb forces should be included in theoretical studies of the vibrational properties of many glasses.

ISSN:0094-243X    

DOI:10.1063/1.30757

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The infrared absorption of materials like amorphous silicon and germanium shows that the atoms have first‐order effective charges although the corresponding crystals do not. This paper demonstrates that these charges originate in the second‐order effective charges of the crystals which are converted in the amorphous phases to first‐order charges by the distortion of the interatomic coordinates. The intensities of the amorphous‐phase fundamental spectra are therefore related to the intensities of the binary combinations of the crystals and the mean square displacements of the atoms required to form the amorphous phases, and they can be used to determine the displacements. For the same model, the difference of the second moments of the density of states for the amorphous and crystalline phases is a sum over some of the fourtorder potential constants. Literature spectra of silicon and germanium have been analyzed, and give root‐mean‐square atomic displacements of 0.59 and about 0.25–032 A˚ respectively.

ISSN:0094-243X    

DOI:10.1063/1.30758

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Thin films of binary borosilicate and phosphosilicate glasses of composition varying from one end‐component to the other can be deposited by reacting Ar‐diluted mixtures of B2H6‐SiH4O2and PH3‐SiH4‐O2on heated Si substrates at 300–450 °C. Room temperature infrared transmission spectra in the range 4000−250 cm−1of these vapor‐deposited dielectric glass films have been studied systematically as a function of film composition. A detailed analysis shows that compositional dependence of the intensity of the bands associated with a B‐O‐Si mode in the borosilicate and a P‐O‐Si mode in the phosphosilicate system conforms to a simple random network model consisting of (1) Si in 4‐fold coordination with oxygens, all of which are bridging a pair of Si and/or B (P) atoms; (b) B in 3‐fold coordination with O and (c) P in 4‐fold coordination with oxygens, one of which is doubly bonded to form a terminal P=O.

ISSN:0094-243X    

DOI:10.1063/1.30759

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We present results for vibrational densities of states and for Raman and infrared spectra calculated for relatively large model structures for amorphous selenium and germanium. Simple force constant models, with parameters fixed by reference to crystalline spectra are used. The results for selenium reproduce essential features of the observed Raman spectra. The germanium results accord with past results on smaller models.

ISSN:0094-243X    

DOI:10.1063/1.30761

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

We show that the vibrational properties of a compound amorphous material (i.e., SiO2) can be calculated by embedding a small molecular unit in a structureless effective medium whose properties are determined self‐consistently.

ISSN:0094-243X    

DOI:10.1063/1.30762

出版商:AIP    

年代:1976

数据来源: AIP