Electrical Properties of Zirconium Ditelluride Single ...

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thermoelectric power, four probe resistivity and Hall parameters along the cleavage plane have been carried out and .... H. Maier and D.R. Daniel, J. Electron.
Electrical Properties of Zirconium Ditelluride Single Crystals D. N. Bhavsar, A. K. Dasadia, B. B. Nariya, M. K. Bhayani, and A. R. Jani Citation: AIP Conf. Proc. 1349, 1085 (2011); doi: 10.1063/1.3606239 View online: http://dx.doi.org/10.1063/1.3606239 View Table of Contents: http://proceedings.aip.org/dbt/dbt.jsp?KEY=APCPCS&Volume=1349&Issue=1 Published by the American Institute of Physics.

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Electrical Properties of Zirconium Ditelluride Single Crystals D. N. Bhavsar, A. K. Dasadia, B. B. Nariya, M. K. Bhayani and A. R. Jani Department of Physics, Sardar Patel University, Vallabh Vidyanagar-388 120, Gujarat, INDIA. Email: [email protected] Abstract. Electrical properties of zirconium ditelluride single crystals have been measured. The measurements of thermoelectric power, four probe resistivity and Hall parameters along the cleavage plane have been carried out and the experimental data have good agreement with reported data. The p-type nature of the grown samples has been confirmed from the Hall Effect and thermoelectric power measurements. Keywords: Electrical properties, Seebeck coefficient.

PACS: 72.50.-i, 72.20. Pa down to room temperature at the same rate 30 K/hr and then switched off. As a result fine free flowing; shiny homogenous polycrystalline material was achieved for each compound. The ampoule was then inserted into a two-zone horizontal furnace. The front zone (reaction zone) of the furnace was maintained at 1243K while the back zone (growth zone) was kept at 1293K for the growth of ZrTe2 single crystal. As a result we get crystals of ZrTe2 after the period of 118 hours. In the present study resistance has been measured along the cleavage plane with the help of multimeter (model 2700, Make: KEITHLEY). The measurements were carried out in the temperature range from 308K to 533K at an interval of 5K. The resistivity of the samples was calculated by using the formula RA (1)  l Hall-Effect measurement was performed along the cleavage plane of as grown crystals of ZrTe 2 in order to determine the type of the semiconductor, mobility and carrier concentration. Knowing the value of difference in resistance (∆R), magnetic field (∆B) and thickness of the sample the Hall coefficient, mobility and charge carrier concentration is evaluated using the relations

INTRODUCTION Transition metal dichalcogenides MX2 (M = Zr, Ti, Hf, Nb, Ta and X = S, Se & Te) that crystallize in the shape of parallel fiber constitute a diversified family ranging from superconductors to wide band gap semiconductor. Here we have grown ZrTe2 crystals by chemical vapour transport method using iodine as a transporting agent [1, 2]. Resistivity measurements were carried out using four probe technique [3, 4] and Hall Effect measurements were performed in order to determine conductivity, mobility and carrier concentration along the chain axis of as grown ZrTe2 crystals [5, 8]. The greatest application of the Seeback effect is in thermoelectric thermometry. This results from the fact that thermoelectric circuits convert thermal energy. The study of thermo electric power provides an independent way to determine the carrier sign, density and position of Fermi level in semiconductors [8, 9, 10, 11, 12 ]. In this report we present results on thermoelectric power measured in temperature range 303K-533K.

EXPERIMENTAL Single crystals of ZrTe2 were prepared by chemical vapour transport method using the iodine as a transporting agent. In the present work author had first prepared the charge of the compounds of ZrTe2. In the present case, the required temperature was 1243K. The ampoule was kept at this constant temperature for 3 days. After this period, the furnace was slowly cooled

R H  μH  ρ

(2)

1 RHe

(3)

η

Solid State Physics, Proceedings of the 55th DAE Solid State Physics Symposium 2010 AIP Conf. Proc. 1349, 1085-1086 (2011); doi: 10.1063/1.3606239 © 2011 American Institute of Physics 978-0-7354-0905-7/$30.00

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μH 

t ΔR  ΔB ρ

0.3

(4) 0.25

The thermoelectric power (TEP) measurements were carried out using the thermo-power (S) measurements set-up TPSS-200 developed by Scientific Solutions, Mumbai. In all the measurements ∆T was kept as 5K and the TEP (S║) measurements were carried out in the temperature range 303K-533K. Due to experimental limitations, TEP (S ┴) measurements normal to the basal plane i.e. parallel to c-axis could not be made.

S (mV/K)

0.2

0.15

0.1

0.05

0 1.87

2.07

2.27

2.47

2.67

2.87

3.07

3.27

1000/T (K-1)

RESULTS AND DISCUSSION

Figure2. Variation of thermoelectric power with inverse of temperature for ZrTe2 single crystals.

The resistivity normal to the basal plane decreases with increase in the temperature which indicates the semiconducting behavior of the as grown crystals. The results obtained from above measurement are shown in figure1.

The positive values of Seeback coefficient indicate that crystal of ZrTe2 is p-type in nature and majority charge carriers in them are holes.

CONLUSIONS The resistivity along the chain axis decreases with increase in the temperature which indicates the semiconducting nature of the grown crystals. The positive value of the hall coefficient and seebeck coefficient confirms that ZrTe2 crystals are p type in nature and majority charge carriers in them are holes.

2.1 1.9

Log (ohm-cm)

1.7 1.5 1.3 1.1 0.9

REFERENCES

0.7 0.5 1.8

2

2.2

2.4

2.6

2.8

3

3.2

3.4

1. Grimmeiss H G, Rabenau A, Hann H and Neiss P, Z, Electrochem, 65, 776(1961) 2. I.P. Akimchenco and G. K. Rasnlova, Sov. Phys. Solid State, 25, 1514(1983). 3. Srivastava S K and Avansthi B N, J, Mater. Sci. 27, 3693(1992). 4. Wilson J A and Yoffe A D ,Adv. Phys., 19, 169(1969). 5. Bratts L and Kjekshus A ,Acta Cehm. Scand, 26, 3441(1972). 6. Stephens P W and Majkrzak C F ,Phys. Rev. B, 33, 1(1986). 7. H. Maier and D.R. Daniel, J. Electron. Mater. 6,

1000/T(K-1)

Figure1. Variation of log ρ Vs 1000/T for ZrTe2 single crystals. From the sign of Hall coefficient, the nature of charge carriers in the grown crystals can be ascertained. All the results obtained from the Hall effect measurements are given in Table1. TABLE 1. Various electrical properties of ZrTe2 crystals. Resistivity (-cm) 1.35092 Hall Coefficient (cm3 -coulomb-1) Carrier Concentration (cm-3) Mobility (cm2/volt-sec)

1.2310×103 5.07×10

693 (1977). 8. Y.G. Yue, A.S. Yue and O.M. Stafsudd, J. Cryst. Growth 54, 248 (1981). 9. G. Lucovsky, R. M. White and J. F. Revelli: Phys. Rev. B 42 (1973) 3859[APS]. 10. J. M. Ziman: Electrons and Phonons (Oxford University Press, London, 1962) Chap. 9. 11. Y. Koike, M. Okamura, T. Nakanomyo and T. Fukase: J. Phys. Soc. Jpn. 52 (1983) 597[IPAP]. 12. D. K. G. de Boer, C. G. van Bruggen, G. W. Bus, R. Coehoorn, C. Haas, G. A. Sawatzky, H. W. Myron, D. Norman and H. Padmore: Phys. Rev. B 29 (1984) 6797[APS].

15

2.7015×106

The positive values of Hall coefficient clearly point out that single crystal of ZrTe2 is p-type and majority carriers in it are holes. The variation of S with temperature in the range 303K to 533K is shown in figure2.

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