T Kavetskyy, Ya Shpotyuk - Medium-range ordering effects in pseudo-binary vitreous as2s3-sb2s3 studied with conventional xrd analysis - страница 1

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ВІСНИК ЛЬВІВ. УН-ТУ

Серія фіз. 2009. Bun. 43. С. 179-184

VISNYKLVIV UNIV. Ser. Physics. 2009. Is. 43. P. 179-184

УДК 539.216.2

PACS number(s): 61.10.Nz, 61.18.-j, 61.43.Fs

MEDIUM-RANGE ORDERING EFFECTS IN PSEUDO-BINARY VITREOUS As2S3-Sb2S3

STUDIED WITH CONVENTIONAL XRD ANALYSIS

T. Kavetskyy1,2, Ya. Shpotyuk2,3

1Solid-State Microelectronics Laboratory, Drohobych State Pedagogical University 24 Franko Str., Drohobych 82100, UKRAINE 2Institute of Materials, Scientific Research Company "Carat" 202 Stryjska Str., Lviv 79031, UKRAINE 3Department of Electronics, Ivan Franko National University of Lviv 50 Dragomanova Str., Lviv 79005, UKRAINE shpotyuk@novas.lviv.ua

In the present work, the medium-range ordering (MRO) effects in pseudo-binary vitreous As2S3-Sb2S3 are studied with conventional x-ray diffraction measurements. It is found that Sb atoms essentially affect on the MRO scale determined by structural correlation length L. As a result, the packing factor of layer configurations p increases with increasing Sb content in the amorphous alloys studied, this effect being enhanced after y-irradiation

Key words: chalcogenide glasses, medium-range order, x-ray diffraction, first sharp diffraction peak, structural correlation length, As2S3-Sb2S3.

Two scales can be recognized in the structure of glasses [1]. The first one is quite short and well defined with a relatively good approximation and documented as short-range ordering (SRO). The other scale is more complicated to be determined due to longer distances (20-50 A and/or more) and it documented by many researchers as medium-range ordering (MRO). Sometimes, the latter can be also shifted to the extended-range ordering (ERO), but the origin of extended structural correlations in the network glasses has been unknown yet.

In the present study, we focus our attention on the MRO scale, the structural correlation length of which L can be estimated on the basis of full width at half maximum (FWHM) of the first sharp diffraction peak (FSDP) in x-ray diffraction (XRD) analysis:

L = 2n /AQfsdp, (1) where AQfsdp is the FWHM of the FSDP in [A1], calculated from p fsdp measured in [deg.] using the relationship between the scattering vector Q [A1] and Bragg angle 8 [deg.] in the form of Q = 4n sin8 /X (X is the x-ray wavelengths).

Also, information on the MRO structural motif can be obtained from the packing factor of amorphous layer configurations p = DS/dS, where DS is an average thickness of the domain built by packing a number of disordered layers determined with the formula

[2]:

© Kavetskyy T., Shpotyuk Ya., 2009

Ds = {KX/Pfsdp cos©FSDP>-{360/2n>, (2) where K = 0,9 is the Debye-Scherrer constant, X is the x-ray wavelengths, ©FSDP is the position of the FSDP and dS is the interlayer distance (dS = X /2sin©FSDP).

The glasses from pseudo-binary (As2S3)x(Sb2S3)1-x (x = 0,9, 0,8, 0,7) system are chosen for analysis in order to find the effect of Sb addition into a glass-forming network on the MRO structural correlations. The experimental measurements of the FSDP profiles in the range of 10° < 2© < 30° were carried out using conventional HZG-4a x-ray diffractometer (Cu Ka-radiation) with 0,05° step. The samples were tested in the rotation regime. The FSDP parameters, position 2©FSDP and FWHM pFSDP, were estimated with accuracy of ±0,1°. To verify Sb-effect, the same glasses were also studied after irradiation by high-energy 60Co y-quanta with average energy of 1,25 MeV and accumulated dose of 1,23 MGy.

The main physical properties of the investigated alloys are summarized in table 1. One can see the strong compositional dependence of the glass transition temperature Tg, optical band gap energy Eg, crystallization temperature Tc, and microhardness H for (As2S3)x(Sb2S3)1-x glasses. It is noticeable that with increasing of Sb content the values of Tg and H increase and the values of Eg and Tc decrease.

Table 1

Physical properties of glasses in (As2S3)x(Sb2S3)1-x system [3-5]

Glass composition

Physical properties

X

1-x

Chemical formula

Tg, K [4]

Tg*, K [4]

Eg, eV [3]

Eg, eV [4]

Tc,

K [4]

H,

GPa

[5]

1,00

0,00

As40S60

487

487,0

2,23

2,15

 

1,32

0,90

0,10

As36Sb4S60

 

 

 

 

 

1,32

0,80

0,20

As32Sb8S60

 

 

2,14

 

 

1,36

0,75

0,25

As30Sb10S60

485

490,0

2,12

1,97

 

 

0,70

0,30

As28Sb12S60

 

 

 

 

 

 

0,60

0,40

As24Sb16S60

 

 

2,05

 

 

1,42

0,50

0,50

As20Sb20S60

487

491,0

2,00

1,90

584

1,45

0,40

0,60

As16Sb24S60

 

 

1,90

 

 

1,50

0,25

0,75

As10Sb30S60

491

492,5

1,86

1,80

532

 

0,20

0,80

As8Sb32S60

 

 

1,85

 

 

1,50

0,10

0,90

As4Sb36S60

493

495,5

 

1,61

516

 

0,00

1,00

Sb40S60

 

 

1,73

 

 

1,59

Note. 1) The glass compositions in the glass-forming region (0<x<0,62 [6]) are marked by bold. 2) The Tg values are obtained using the relation: Tg =520,8-15,72 Eg [4].

Structural study of (As2S3)x(Sb2S3Vx (x = 0,9, 0,8, 0,7) alloys demonstrates the strong Sb-effect on the MRO scale. Figure 1 shows the FSDP-related XRD patterns for the investigated glasses in non-irradiated and y-irradiated states. The MRO parameters PFSDP, L, DS, dS, and p = DS/dS are gathered in table 2.

Fig. 1. The FSDP-related XRD patterns for (As2S3)x(Sb2S3)1-x glasses (x = 0,9, 0,8, 0,7) in non-irradiated (closed symbols) and y-irradiated (open symbols) states

Table 2

The MRO parameters for (As2S3)x(Sb2S3)1-x glasses (x = 0,9, 0,8, 0,7) in non-irradiated (non-irrad.) and y-irradiated (irrad.) states

MRO parameters (± 0,1)

(As2S3)x(Sb2S3)1-x

 

x = 0,9

x = 0,8

x = 0,7

 

Sample conditions

 

non-irrad.

irrad.

non-irrad.

irrad.

non-irrad.

irrad.

AsDP (°)

5,6

5,0

4,6

4,0

4,3

3,6

L (A)

15,7

17,4

19,0

22,4

20,3

24,2

Ds (A)

14,4

16,1

17,5

20,1

18,7

22,4

ds (A)

5,1

5,1

5,1

5,0

5,0

5,1

p = Ds/ds

2,92

3,16

3,43

4,02

3,74

4,39

It is established that impact of Sb is mainly due to increase MRO structural correlation length L and packing factor of amorphous layer configurations p, it enhancing after irradiation. In order to estimate percentage of the medium-range ordering effects observed we calculate the radiation-induced change in the packing factor Ap/p in percents (fig. 2). The effect is found to be increased from 12,1 to 17,4 % when the molar fraction of As2S3 x in (As2S3)x(Sb2S3)1-x system changes from 0,9 to 0,7.

Fig. 2. The "packing"-factor p calculated for (As2S3)x(Sb2S3)1-x glasses (x = 0,9, 0,8, 0,7) in non-irradiated (closed symbols) and y-irradiated (open symbols) states (the dashed arrows indicate the relative radiation-induced change in the packing factor Ap/p in percents)

In conclusion, by studying the medium-range ordering effects in pseudo-binary vitreous As2S3-Sb2S3 with conventional XRD measurements, it is found that Sb atoms essentially affect on the MRO scale determined by the structural correlation length L. As a result, the packing factor of amorphous layer configurations p increases with increasing Sb content in the alloys studied, the effect is enhanced after y-irradiation of the samples.

This work is supported by Fundamental Researches State Fund of the Ministry of Education and Science of Ukraine (Project No. F25.2/138) and Science and Technology Centre in Ukraine (Project N 3745).

1. Cervinka L. Several remarks on the medium-range order in glasses // J. Non-Cryst. Solids. 1998. Vol. 232-234. P. 1-17.

2. LorincziA. Effect of ultraviolet radiation on the Ge27Sb13Se60 amorphous films // J. Optoelectron. Adv. Matter. 1999. Vol. 1. P. 37-42.

3. El Idrissi Raghni M.A.., Lippens P.E., Olivier-Fourcade J. et al. Local structure of glasses in the As2S3-Sb2S3 system // J. Non-Cryst. Solids. 1995. Vol. 192-193. P.

191-194.

4. NDri K., Sei J., Houphouet-Boigny D., Jumas J. C. Theoretical investigation of the structural properties of Sb2S3-As2S3 and Sb2Te3-As2S3 glasses // Chalcogenide Letters. 2007. Vol. 4. P. 101-107.

5. Kothiyal G.P., Kumar R., Goswami M., Shrikhande V.K. et al. Preparation of mixed arsenic/antimony chalcogenide glasses and some optical and thermo-physical properties // J. Non-Cryst. Solids. 2007. Vol. 353. P. 1337-1340.

6. Чернов А.П., Виноградова Г.З., Шелкова А.Ф. и др. Исследование системы As2S3-Sb2S3 // Журн. неорган. хим. 1977. Т. 22. № 1. С. 198-200.

ЕФЕКТИ СЕРЕДНЬОГО ПОРЯДКУ В ПСЕВДОБІНАРНИХ СКЛОПОДІБНИХ СПЛАВАХ СИСТЕМИ As2S3-Sb2S3: АНАЛІЗ МЕТОДОМ ТРАДИЦІЙНОЇ РЕНТГЕНІВСЬКОЇ ДИФРАКЦІЇ

T. Кавецький1'2, Я. Шпотюк2'3

1 Лабораторія матеріалів твердотільної мікроелектроніки Дрогобицький державний педагогічний університет імені Івана Франка вул. І. Франка 24, 82100 Дрогобич, Україна 2Інститут матеріалів, Науково-виробниче підприємство "Карат " вул. Стрийська 202, 79031 Львів, Україна 3Факультет електроніки Львівський національний університет імені Івана Франка вул. Драгоманова 50, 79005 Львів, Україна

Вивчено ефекти середнього порядку (СП) в псевдобінарних склоподібних сплавах системи As2S3-Sb2S3 за допомогою методу традиційної рентгенівської дифракції. З'ясовано, що атоми Sb суттєво впливають на шкалу СП, якавизначається структурною кореляційною довжиною L. Тому з підвищенням вмісту Sb в досліджуваних сплавах зростає фактор упаковки аморфних шаруватих конфігурацій p, причому більш інтенсивно після y-опромінення зразків.

Ключові слова: халькогенідні стекла, середній порядок, рентгенівська дифракція, перший різкий дифракційний пік, структурна кореляційна довжина

As2S3-Sb2S3.

ЭФФЕКТЫ СРЕДНЕГО ПОРЯДКА В ПСЕВДОБИНАРНЫХ СТЕКЛОВИДНЫХ СПЛАВАХ СИСТЕМЫ AS2S3-SB2S3:

АНАЛИЗ МЕТОДОМ ТРАДИЦИОННОЙ РЕНТГЕНОВСКОЙ ДИФРАКЦИИ

T. Кавецкий1,2, Я. Шпотюк2,3

1 Лаборатория материалов твердотельной микроэлектроники Дрогобычский государственный педагогический университет имени ИванаФранко ул. И. Франко 24, 82100 Дрогобыч, Украина 2Институт материалов, Научно-производственное предприятие "Карат" ул. Стрыйская 202, 79031 Львов, Украина 3Факультет электроники Львовский национальный университет имени Ивана Франко ул. Драгоманова 50, 79005 Львов, Украина

Изучены эффекты среднего порядка (СП) в псевдобинарных стекловидных сплавах системы As2S3-Sb2S3 с помощью метода традиционной рентгеновской дифракции. Установлено, что атомы Sb существенно влияют на шкалу СП, которая определяется структурной корреляционной длиной L. Поэтому при повышении содержания Sb в исследуемых сплавах растет фактор упаковки аморфных слоистых конфигураций p, причем более интенсивно после у-облучения образцов.

Ключевые слова: халькогенидные стекла, средний порядок, рентгеновская дифракция, первый резкий дифракционный пик, структурная корреляционная длина As2S3-Sb2S3.

Стаття надійшла до редколегії 04.06.2008 Прийнята до друку 25.03.2009

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T Kavetskyy, Ya Shpotyuk - Medium-range ordering effects in pseudo-binary vitreous as2s3-sb2s3 studied with conventional xrd analysis