Structural and Thermodynamic Properties of Pb-Cd-Te Thin Films: Experimental Study and DFT Analysis
- PDF / 2,337,286 Bytes
- 12 Pages / 593.972 x 792 pts Page_size
- 6 Downloads / 175 Views
https://doi.org/10.1007/s11664-020-08561-5 Ó 2020 The Minerals, Metals & Materials Society
Structural and Thermodynamic Properties of Pb-Cd-Te Thin Films: Experimental Study and DFT Analysis B. NAIDYCH ,1,5 T. PARASHCHUK,1,4 I. YAREMIY,1 M. MOYSEYENKO,2 O. KOSTYUK,1,2 O. VOZNYAK,1 Z. DASHEVSKY,3 and L. NYKYRUY1 1.—Vasyl Stefanyk Precarpathian National University, Shevchenko Str. 57, IvanoFrankivsk 76018, Ukraine. 2.—Ivano-Frankivsk National Medical University, Halytska Str. 2, Ivano-Frankivsk 76000, Ukraine. 3.—Ben-Gurion University of the Negev, 84105 BeerSheva, Israel. 4.—Present address: The Lukasiewicz Research Network – Krakow Institute of Technology, Zakopianska Str. 73, 30-418 Krako´w, Poland. 5.—e-mail: [email protected]
Vacuum evaporation technology was applied to fabricate Pb0.9Cd0.1Te:Pb (3 at.%) thin films on glass and polycrystalline silicon substrates. X-ray diffraction analysis confirms the rock salt structure with the (100) preferred growing direction for the investigated films. The formation of films on an amorphous glass substrate occurs by two consecutive growth mechanisms. The Volmer– Weber mechanism is the initial mechanism, and it gradually changes with the Frank–van der Merve mechanism. On the polycrystalline silicon substrate, the Volmer–Weber growth mechanism is dominant. Surface formations are oriented and needle-like. A complex of thermodynamic parameters: the enthalpy of formation, entropy, Gibbs free energy, and heat capacity were calculated using the estimated crystallographic data. This work brings light on the fabrication process of single-phase Pb0.9Cd0.1Te:Pb (3 at.%) thin films with a high-quality surface using the low-cost and simple vacuum evaporation method. Key words: Thin films, thermodynamic properties, ab initio calculations, XRD analysis, solid solution
INTRODUCTION Pb-Cd-Te solid solution is a promising material for the fabrication of thermoelectric modules over a medium temperature range.1 Due to the isoelectronic effect of cadmium (Cd) atoms in lead telluride (PbTe), this material can be used for the fabrication of both n- and p-type thermoelectric legs.2 Thin films based on Pb-Cd-Te are extremely interesting for application in miniature devices or various flexible systems, such as thermoelectric micromodules.3,4 The microstructure has a decisive influence on the properties of thin films.5 On the other hand, deposition and heat treatment technologies are
(Received April 26, 2020; accepted October 10, 2020)
reliable for achieving suitable and stable characteristics. If the dimensionless figure of merit for bulk materials is sufficiently high, this parameter for thin films is still a challenge.5–8 The solubility limit of Cd in the PbTe matrix can be up to 15%.9,10 The formation of such a solid solution is atypical because of the significant difference of its components in the crystal structures (sphalerite for CdTe and rock-salt-type for PbTe) and the bandgaps [Eg (CdTe) = 1.534 eV11 and Eg (PbTe) = 0.31 eV12]. On the other hand, the formation of the single-phase sol
Data Loading...
