Effect of impurities on morphology, growth mode, and thermoelectric properties of (1 1 1) and (0 0 1) epitaxial-like ScN films

Abstract

ScN material is an emerging semiconductor with an indirect bandgap. It has attracted attention for its thermoelectric properties, use as seed layers, and for alloys for piezoelectric application. ScN or other transition metal nitride semiconductors used for their interesting electrical properties are sensitive to contaminants, such as oxygen or fluorine. In this present article, the influence of depositions conditions on the amount of oxygen contaminants incorporated in ScN films were investigated and their effects on the electrical properties (electrical resistivity and Seebeck coefficient) were studied. The epitaxial-like films of thickness 125  5 nm to 155 5 nm were deposited by D.C.-magnetron sputtering on c-plane Al2O3, MgO(111) and r-plane Al2O3 at a substrate temperature ranging from 700 C to 950 C. The amount of oxygen contaminants presents in the film, dissolved into ScN or as an oxide, was related to the adatom mobility during growth, which is affected by the deposition temperature and the presence of twin domain growth. The lowest values of electrical resistivity of 50  cm were obtained on ScN(111)/MgO (111) and on ScN(001)/r-plane Al2O3 grown at 950C with no twin domains and the lowest amount of oxygen contaminant. At the best, the films exhibited an electrical resistivity of 50  cm with Seebeck coefficient values maintained at -40 V K -1 , thus a power factor estimated at 3.2 10 -3 W m -1 K -2 (at room temperature).

Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN2-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations

“…Experimentally, temperature-dependent transport measurements on ScTaN 2 showed a metallic-like behavior by measurement of resistivity as a function of temperature, where it increased with temperature [11], but with high absolute values of resistivity. This is indicative of a highly doped degenerate semiconductor, typical also for ScN [13,14,17,19,50].…”

“…Atomic positions data and experimental lattice parameters (powder X-ray diffraction) of ScTaN 2 [11] and ScNbN 2 [9]. Furthermore, ScN is a semiconductor showing promise for thermoelectric applications due to its suitable thermal and electrical properties [12][13][14][15][16][17]. However, the thermal conductivity is relatively high (8-12 Wm −1 K −1 ) [13,18], leading to a rather low thermoelectric figure of merit (ZT).…”

The effects of microstructure, Nb content and secondary Ruddlesden–Popper phase on thermoelectric properties in perovskite CaMn1−xNbxO3 (x = 0–0.10) thin films

“…The Seebeck coefficient at room temperature was measured at atmospheric pressure using a homemade Seebeck voltage measurement setup. 26 The samples were electrically isolated and placed on two copper electrodes separated by 8 mm, which were connected to the surface of the sample (lm) and the voltage was measured by a multimeter with a resolution of 0.01 mV. A temperature gradient of 42 C was applied using a heated metal tip on one electrode, while the other was kept at room temperature.…”

Theoretical and Experimental Studies on Early Transition Metal Nitrides for Thermoelectrics

“…For fast and accurate room-temperature analysis of the Seebeck coefficient, an inhouse setup 64 Typical thermoelectric materials are narrow band-gap semiconductors, for increased electrical conductivity. High electron mobility is also required ( ≈ 2,000 cm 2 (V • s) −1 ), but the carrier concentration should be comparatively low so that both the electrical conductivity and the Seebeck coefficient can be addressed.…”