Physica status solidi: Volume 7, Number 2 November 1 [Reprint 2021 ed.] 9783112497067, 9783112497050

Citation preview

plrysica status solidi

V O L U M E 7 . N U M B E R 2 • 1964

Contents Review Article B. T.

KOLOMIETS

Pag« Vitreous Semiconductors (I)

359

Original Papers M . BOÖEK u n d G . HÖTZSCH

Die plastische Verformung von kadmiumlegierten Zinkeinkristallen (II) 373 H . HOFFMANN

Magnetische Feinstruktur und magnetische Eigenschaften einachsiger ferromagnetischer Schichten (II) 383

P . S. MAHESH a n d B . DAYAL

The Debye-Waller Factors of Copper and Gold by de Launay's Method 399 V . GALLINA a n d M . OMINI

Vacancy as a Phonon Field Perturbation (IV) K . BAIEBLEIN

A.

405

Untersuchung über die Streuung langsamer Neutronen an bestrahltem Quarz und Beryllium 415

J l y ß i e H K O H E . M. r i a B J i H K MeToa jiyHKizHü TpHHa B TeopHH HajiyweHHH CBeTa npwMecHbiMH ueHTpaMn TBepnoro Tejia 433

K . GODWOOD, M . LEFELD-SOSNOWSKA a n d E .

ZIELINSKA-ROHOZINSKA

Observations of the "Pendellösung" Fringes with the Three-Crystal X-Ray Spectrometer 445 M . LEFELD-SOSNOWSKA

Measurement of the Mean and Anomalous Absorption Coefficients with the Three-Crystal X - R a y Spectrometer 449 B . LENGELEB a n d W . LUDWIG

Localized Vibrational Modes at Plane Faces of Defects in Crystal Lattices 463 CH. SCHWINK

Untersuchungen des Fließbereichs neutronenbestrahlter Kupfereinkristalle (III) 481

G . REMAUT, A . LAGASSE, a n d S . AMELINCKX

Electron Microscopic Study of the Domain Structure in Anti-Ferromagnetic Cobalteous Oxide 497 Z.

GYULAI

Die Bildung von Kristallkeimen in übersättigten Alkalihalogenidlösungen als Folge von mechanischen Stößen 511 (Continued on caver three)

physica status solidi B o a r d of E d i t o r s P. A I G R A I N , Paris, S. A M E L I N C K X , Mol-Donk, W. D E K E Y S E R , Gent, W. F R A N Z , Münster, P. G Ö R L I C H , Jena, E. G R I L L O T , Paris, R. K A I S C H E W , Sofia, P. T. L A N D S B E R G , Cardiff, L. N f i E L , Grenoble, A. P I E K A R A , Poznan, A. S E E G E R , Stuttgart, 0. S T A S I W , Berlin, M. S T E E N B E C K , Jena, F. S T Ö C K M A N N , Karlsruhe, G. S Z I G E T I , Budapest, J. T A U C , Praha Editor-in-Chief P. G Ö R L I C H Advisory Board M. B A L K A N S K I , Paris, P. C. B A N B U R Y , Reading, M. B E R N A R D , Paris, W. B R A U E R , Berlin, W. C O C H R A N , Cambridge, R. C O E L H O , Fontenay-aux-Roses, H.-D. D I E T Z E , Aachen, J. D. E S H E L B Y , Birmingham, G. J A C O B S , Gent, J. J A U M A N N , Köln, E. K L I E R , Praha, E. K R O E N E R , Clausthal-Zellerfeld, M. MATYÄS, Praha, H. D. M E G A W , Cambridge T. S. MOSS, Camberley, E. N A G Y , Budapest, E. A. N I E K I S C H , Jülich, L. P A L , Budapest, M. R O D O T , Bellevue/Seine, B. V. R O L L I N , Oxford, H. M. R O S E N B E R G , Oxford, R. V A U T I E R , Bellevue/Seine

Volume 7 • Number 2 • Pages 357 to 710 and K 57 to K 140 November 1, 1964

A K A D E M I E - V E R L A G

- B E R L I N

Subscriptions and orders for single copies should be addressed to AKADEMIE-VERLAG GmbH, Berlin W 8, Leipziger Straße 3—4 or to Buchhandlung KUNST UND WISSEN, Erich Bieber, 7 Stuttgart S Wilhelmstr. 4 — 6 or to Deutsche Buch-Export und -Import GmbH, Leipzig C 1, Postschließfach 276

Editorial Note: "physica status solidi" undertakes that an original paper accepted for publication before the of any month will be published within 50 days of this date unless the author requests a postponement. In special cases there may be some delay between receipt and acceptance of a paper due to the review and. if necessary, revision of the paper.

Schriftleiter und verantwortlich für den Inhalt: Professor Dr. Dr. h. c. P. Görli c h , Berlin C 2, Neue Schönhauser Str. 20 bzw. Jena, Humboldtstr. 26. Redaktionskollegium: Dr. S. O b e r l ä n d e r , Dr. E. G u t s c h e , Dr. W. B o r c h a r d t . Anschrift der Schriftleilung: Berlin C 2, Neue Schönhauser Str. 20, Fernruf: 426788. Verlag: Akademie-Verlag GmbH, Berlin W 8, Leipziger Str. 3 - 4 , Fernruf: 220441, TeJex-Nr. 011773, Postscheckkonto: Berlin 35021. — Die Zeitschrift „physica status solidi" erscheint jeweils am 1. des Monats. Bezugspreis eines Bandes MDN 60,-. Bestellnummer dieses Bandes 1068/7. Für l'>64 sind 4 Bande vorgesehen. Gesamtherstcllung: VLB Druckerei „Th>mas Müntzer" Bad Laugensalza. — Veröffentlicht unter der Lizeoznummer 1310 des Presseamtes beim Vorsiizenden des Ministerrates der Deutschen Demokratischen Republik.

Review

Article

phys. s t a t . sol. 7, 359 (1964) A. F. Joffe Physical

Technical Institute,

Academy of Sciences of the USSR,

Leningrad

Vitreous Semiconductors (I) By B . T . KOLOMIETS

Contents 1.

Introduction

2. Region

of glass

formation

properties of chalcogenide 3. Physicochemical 3.1 Density 3.2 Structure 3.3 Viscosity 3.4 Softening temperature 3.5 Microhardness 3.6 Coefficient of linear expansion 3.7 Chemical durability 3.8 Stability 4. Optical properties of chalcogenide glasses

glasses

properties 5. Electrical 5.1 Conductivity 5.2 Sign of current carriers and of thermal e.m.f. 5.3 Dependence of conductivity on composition 5.4 Conductivity and impurities 5.5 Concentration and mobility of current carriers 5.6 Temperature dependence 5.7 Dielectric constant 5.8 Effect of gamma radiation 6. Photoelectric properties 6.1 Photoconductivity 6.2 Photo - e.m.f. 7. Change

of properties

8. Oxychalcogenide References

during

the glass-crystal

transition

glasses

1. Introduction

Glass representing an alloy of a number of metal oxides has found a broad range of applications. Among its properties which are of principal importance from this point of view, are, for example, optical transparency in various spectral regions and air tightness. The electrical properties which will be of main interest to us here have also found use. In the first place it is the low conductivity of glass which permits it to be used as an insulating material. I t would be most desirable to produce glasses possessing a high conductivity. However the highest magnitude of the electric conductivity of oxide glasses obtained up to approximately !) P a r t I I see phys. s t a t . sol. 7, 713 (1964). 24«

360

B . T . KOLOMIETS

1955 did not exceed 10"8 i l - 1 c m 1 , and since the conductivity of such glasses was of ionic nature they could not be used for quite a number of practical purposes. In 1955 articles have appeared which described a new class of glasses obtained on the basis of alloys of metal sulphides, selenides and tellurides. It has been established that the electric conductivity of such glasses is of a purely electronic nature and lies within 10~13 to 10 3 ÎÎ" 1 cm -1 . On the basis of this as well as of some other properties these materials could be classified as semiconductors, and they have the name "vitreous semiconductors". At the same time they are typical glasses, and in order to distinguish them from the oxide type they are ordinarily referred to as "chalcogenide glasses".2) The choice between the two terms, vitreous semiconductors and chalcogenide glasses, will be made further by us depending upon the point of view from which a particular problem will be considered. It should be borne in mind that they are equivalent. The high conductivity of chalcogenide glasses (10~3 Q _ 1 cm - 1 ) as well as the absence of ionic conduction in them, have resulted in an extensive research aimed at studying their electrical and physicochemical properties and locating the boundaries of the vitreous state [2, 6,10,12, 49, 50, 53,54,55]. Presented below are some results of the corresponding investigations carried out at the Joffe PhysicoTechnical Institute of the USSR Academy of Sciences. Some data have been taken from works being conducted at the Leningrad State University. The investigation of chalcogenide glasses was at first closely associated with the research into the nature of ternary semiconducting compound systems. It has been established that in one of them, namely in the system Tl2Se-Sb2Se3, the equimolecular alloy Tl2Se-Sb2Se3 represents a new chemical compound with typical semiconducting properties. Further research aimed at the investigation of the relationship between the electrical properties and composition for an isomorphous substitution of arsenic for antimony revealed the unexpected fact, that after the completion of this substitution the resulting alloy Tl2-Se-As2Se3 did not exhibit a crystalline structure and was a typical glass by quite number of properties [1], These properties were: the absence of lines in X-ray diffraction patterns and the absence of the break in the cooling curves obtained by thermal analysis; the fracture, brittleness, and viscosity typical for glass and permitting to draw the material out into threads and to blow out thin films. The glass of this composition has become a fore-runner of a new group of glasses, and because of this as well as due to a number of its interesting properties was taken as a starting material in the series of investigations reported below. Its conductivity is 10"9 Q - 1 cm"1. The substitution of tellurium in this alloy for selenium has revealed that over all the concentration region extending from Tl2Se-As2Se3 to Tl2Se • As2Te3 the materials remain in the vitreous state, the conductivity in the latter case being as high as 10~3 cm - 1 which is most interesting. The results of this investigation have shown that the glass of the composition Tl2Se • As2Se3 is by no means an exception and it represents only one example of a probable large number of similar materials. This consideration initiated a research aimed at establishing the boundaries of the vitreous state in the alloys of chalcogenides of the same metals. 2 ) One uses the term „chalcogens" to denote chemical analogies of oxygen in the Periodic Table, namely sulphur, selenium and tellurium, whereas their compounds with metals are called "chalcogenides".

Vitreous Semiconductors (I)

361

In recent years the investigation of the amorphous state and of amorphous substances has become an interesting branch of research pursued by many experimenters and theorists working in solid state physics. One of the most interesting objects in this research are chalcogenide glasses which, due to the inherent high conductivity, enable, for example, to carry out a complex investigation of properties necessary to draw useful generalizations. One of the features characteristic for this group of vitreous semiconductors is the relative simplicity with which they can be transferred from the vitreous into the crystalline state. This permits to study the variation of properties during the transition from one state of aggregation into another, as well as to investigate the kinetics of crystallization of substances by electrical, X-ray diffraction, and optical techniques. The optical methods which have not yet been explored up to now are waiting for experimenters. 2. Region of Glass Formation The techniques used at the initial stage of research which was aimed at establishing the regions of the vitreous state in the chalcogenide alloys consisted in varying the molecular composition of the compounds of interest. Such an approach was dictated by a number of considerations, and among them by a desire to study the materials later on both in the vitreous and crystalline states. The latter requires, of course, the knowledge of the chemical composition and of the crystal structure of the components. The chalcogenide vitreous semiconductors described here were synthesized from elemental starting materials taken in a predetermined weight ratio and placed in evacuated quartz vials. The individual components were weighed out to 2 X 10~ 4 g. Quartz vials containing the mixture of components were kept in an electric oven for 1 to 2 hours at the melting point of the highest-melting compound forming a part of the glass to be produced, and after that heated up to 850 to 900 °C. After maintaining the vials containing the alloy for one hour at this temperature, they were either slowly cooled down during 12 to 14 hours in the switched-off over or subjected directly to the ambient room temperature, which was equivalent to quenching. The amount of material synthetized in this way was usually of the order of 10 to 20 g. In the majority of cases, the alloys thus obtained were opaque ingots of black color which were then used to prepare specimens for subsequent measurements. As an indication of the glassy state served the absence of lines in the X-ray diffraction patterns and of the break in the cooling curve obtained by thermal analyses, the viscosity and typical fracture-behaviour. Additional checks were provided by the investigation of microstructure in polarized light which permits to detect minute amounts of the crystalline phase in the glass. The work carried out at the first stage of research revealed a large number of vitreous materials in the following systems: 1. As 2 S 3 -As 2 Se 3 , 2. As 2 Se 3 -As 2 Te 3 ,

3. As 2 S 3 -As 2 Te 3 , 4. AS2S3-T12S, 5. As 2 S 3 -Sb 2 S 3 ,

6. As 2 Se 3 -Sb 2 Se 3 , 7. As 2 Se 3 -Tl 2 Se,

and as result of further investigations they were found in some other ternary and quaternary compositions [3,4, 5, 6J.

B . T . KOLOMIETS

362 TLTe

As/e3

/( \\

Tl,S

ASzS3

Tlje

TLSe

fates

1

\

Fig. 1. Regions of glass formation in the alloys of chalcogenides of Tl, As, Sb, P and Bi

As,Te,

Fig. l a and l b give an idea of the number of alloys of chalcogenides of thallium, arsenic, antimony, phosphor, and bismuth which can be obtained as glasses. These figures illustrate experimental data concerning the regions of the vitreous state. Areas confined within the polygons characterize the vitreous state, and those outside them — the crystalline state. In both figures the inner polygon corresponds to the case of a slow cooling after the preparation, and the outer one to the tJiJe} SipSsj BiJj quenching mode of cooling. It is seen from Fig. 1 that the region of vitreous state in the chalcogenide alloys concerned is quite large. The number of materials in these systems which are capable of reaching vitreous state may be apparently much larger since it was found that they allow a considerable deviation from the stoichiometric composition. In the glass Tl 2 Se • As2Se3, for instance, the vitreous state persists with the content of arsenic varying within ¿ 3 0 at.%, selenium within + 4 3 to —14 at.% and thallium within + 3 0 to - 1 0 at.% [3, 7]. Extensive regions of glass formation have been found also in systems containing germanium. Fig. 2 shows the regions of glass formation in the ternary systems As-S-Ge and As-Se-Ge, the corresponding data having been taken from the investigations carried out at the Leningrad State University under the direction of M U L L E R [27, 2 9 ] . Some interesting work on these systems was done also SbJe,

SbS,

5b?Se3

SbJe3

f

b y AYO a n d KOKOKINA [32, 33, 34, 35],

Besside these investigations, studies were also made of the glass formation in compound chalcogenides based on the sulphide and selenide of arsenic which

Vitreous Semiconductors (I)

363

permitted to locate the regions of the vitreous state in a large number of other alloys [4,26,28,30,31]. These studies described in detail below were also aimed at establishing criteria which determine the glass formation in the alloys in question [5,25]. The alloys prepared were based on the sulphide and selenide of arsenic and included sulphides and selenides of elements of the I, I I , I I I , IV-b subgroups of the periodic system (except for boron, aluminium, carbon, and silicon). The composition of alloys was chosen along the section lines of the ternary systems Me-x-As, where Me stands for the elements of the I, I I , I I I and IV groups, and x — for sulphur or selenium. The investigated systems were: for the elements of the first group — Me2xA S 2 X 3 ; for the second — Mex-As 2 x 3 ; for the third — Me2x3-As2x3; and for the fourth — Mex2-As2x3. Alloys were prepared at compositional intervals of about 5 mol%. As the boundary of the glass-forming region was taken the composition of an alloy producing glass at a cooling rate of 200 °C/s and crystallizing at a rate of 1 °C/min. Alloys in which the microstructural analysis revealed crystallization during cooling were in the majority of cases di- or multiphasal substances. One side of the compositional triangles of all ternary alloys was the system As-x in which the boundaries of the glass forming region were connected with straight lines with the point determining the boundary of the glass formation in the corresponding pseudobinary section. In this way we obtained approximate data on the regions of glass formation in ternary compounds and could compare these regions by calculating the areas of figures traced by the techniques described. Fig. 3 shows the regions of glass formation for selenides (sulphides yielded results which lie close to these).

Fig. 3. Regions of glass formation in the systems: a) Elements of the 1st group — Cu, Ag, Au. c) Elements of the 3rd group — Ga, In, Tl. b) Elements of the 2nd group - Zu, Cd, Hg. d) Elements of the 4th group — Ge, Sn, Pb. (In c) read Tl 2 Sc instead of the lower In 2 Se 3 )

364

B . T . KOLOMIETS

It is seen from the figures that in general the glass forming regions in the alloys investigated are not large. An attempt to correlate the obtained results with the criteria proposed for compound oxide-based alloys by Z A C H A R I A S E N and W I N T E R K L E I N proved a failure [5]. We considered it expedient to approach the study of the experimental results by investigating the properties of crystal chalcogenides which do not exist in the vitreous state (that is, chalcogenides of the elements of the I, I I , I I I and IV groups), since as their concentration increases, they start to crystallize in the first place in many cases in the original form. Unfortunately a lack of data precluded our using any more convenient characteristics than the heat of formation. However even this parameter revealed a correlation with the extent of the glass-forming region (Fig. 4). This appears to be only natural since the heat of formation for the chalcogenides of the elements of the first three groups permits to make a rough estimate of the chemical bond energy (this is not true for compounds with a more covalent type of bonding). The bond energy permits to characterize the tendency of non-glass forming chalcogenides to the isolation from the melt. The higher the bond energy, the more narrow is the region of glass formation in a compound alloy. Since the non-glass forming chalcogenides of the elements of the first three groups are not, as a rule, of a chain or laminate structure, one may expect that in glasses they occupy places which are not equivalent to the chalcogenides of the elements of the V group from the point of view of their structure. This suggestion is confirmed by the fact that the glass formation of the chalcogenides of these groups in compound alloys follows different laws. Thus the investigation described has resulted in bringing to light new groups of chalcogenide glasses and in the establishment of a relation between the bond energy of the compounds forming a part of the glass and the tendency to glass formation. The problem concerning the criteria of glass formation was considered by a number of prominent scientists. The empirical and formal approach was gradually replaced by attempts at a thorough physical interpretation. The point of view accepted at the present time requires the presence of a covalent bond between the atoms forming a glass in order that the glass formation take place. This condition is contained in an implicit form in the rule suggested by W I N T E K - K L E I N . M Ü L L E R has been the first to propose it in an explicit form [25]. tySe •

*Tl2S

•ZnSe -ZnS

insensé Heat of formation

Fig. 4. Relationship between the heat of formation and the glass formation property. (The point below ZnSe corresponds to CdS)

Vitreous Semiconductors (I)

365

The simplicity of production and the possibility of large alterations of composition in the chalcogenide glasses resulted in investigations aimed at learning the laws governing the glass formation. These investigations which were carried out mainly with the chalcogenides of phosphor, arsenic, and bismuth revealed a weakening of the glass-forming property with an increase of the atomic weight, that is, with the "metallization" of bonding. The conclusion which may be drawn from this work is as follows [5]. The formation of glass is associated with the chemical nature of atoms, the character of electron interaction between them and the resulting peculiarities of the short-range order in the melt. The necessary condition for the glass formation is the existence of strong covalent bonds remaining unchanged during the transition from the solid state to the melt. By retaining their nature in melts, tetrahedral covalent bonds formed according to the rule of G R I M M - S O M M E R F E L D prevent glass formation and present an exception. The metallization of the covalent bonding caused by the increase of the atomic weight also prevents glass formation.

3. Physicochemical Properties of Chalcogenide Glasses 3.1

Density

The density of the chalcogenide glasses is not studied adequately. It may be said that in general it exceeds the density of oxide glasses and depends on composition. For the purpose of illustration, in Table 1 are presented the values of density for the glasses in the system As 2 Se 3 -As 2 Te 3 [2]. Table 1 Density of glasses in the system As2Se3-As2Te3 Composition

Density (g/cm3)

As 2 Se 3 4 As 2 Se 3 • As2Te3 AsgSßg * Asg^Cg As 2 Se 3 • 2 As 2 Te 3 .AsgScg * 3 A-SgTög

3.2

4.58 4.75 4.98 5.19 5.29

Structure

V A I P O L I N has carried out an extensive X-ray structure investigation in order to establish the nature of the structure of the glasses in such simple compounds as AS 2 S 3 , As a Se 3 , and As 2 Te 3 , the latter having been studied only in the crystalline state, and in the systems As 2 S 3 -As 2 Se 3 and As 2 Se 3 -As 2 Te 3 [36, 37]. T A R A S O V with collaborators has used the low-temperature heat capacity method to determine the structure of vitreous As 2 S 3 and A s 2 S e 3 [ 3 8 J . Finally, P O Z D N E V has drawn conclusions on the structure of the glasses in the system As 2 Se 3 As 2 Te 3 on the basis of experimental data on the viscosity in this system [21],

366

B. T.

KOLOMIETS

All these different methods of investigation have brought the authors to a general conclusion that the structure of glasses of this group is of the chain or laminate type. This conclusion cannot however be extended to cover all chalcogenide glasses. This is indicated, for instance, by the fact, that in the course of preparation of some glasses of complex composition sometimes two or even three immiscible vitreous phases are formed. Besides, an investigation of the effect of impurities on the softening temperature, to be described later, indicates a transition from the chain-laminate structure to a three-dimensional one. It follows from the given examples that the structure of chalcogenide glasses depends on chemical composition. The investigation of the structure of the system As2Se3-As2Te3 in the vitreous and crystalline states carried out by VAIPOLIN has shown that the corresponding transition does not result in any significant changes in the atomic positions in As2Se3 whereas in three-component alloys a marked rearrangement of the shortrange order is possible [36]. 3.3

Viscosity

The viscosity of chalcogenide glasses was investigated only for one system, As2Se3-As2Te3, the method used being that of torsional vibrations. The results have shown that the viscosity of semiconducting glasses in this system lies within the range 102 to 10" 1 Stokes at temperatures of about 400 °C, and within 10" 1 to 10" 2 Stokes — at temperatures of about 700 °C. The relationship of viscosity vs. temperature is presented in Table 2, and its compositional dependence in Fig. 5. Table 2 Viscosity of glasses in the system As2Se3-As2Te; 3 .A.S2S&3 * As 2 Te 3

AS2S e3 I(°C)

412 462 480 570 608 640 690

v (Stokes) 15.5 3.3 2.74 0.5 0.29 0.18 0.09