Investigation of the electric properties of Cu₂S single crystals

Abstract

Single crystals of p-Cu,S are obtained with a hole concentration of 7.4~10'*cm-~, a mobility of 25 cmp V-ls-l, and a thermoelectric power of 90 mV/deg. The electrical conductivity, thermoelectric power and Hall effect are measured between 20 and 000 OC. A jump due to structural transformetions is observed in the temperature dependence of these parameters at 125 and 480 O C . The activation energy is found to have a value of 1.8 eV for the intrinsic range of the Conductivity, the value found for the extrinsic range being 0.064 ev. Cu$ is a scantily investigated semiconductor. The great energy gap (AE w w 1.8 eV), high melting point (T, = 1130 "C), mechanical strength, and autoalloying at the expense of structural imperfections make this material an interesting object for investigations.C%S has three modifications, namely a stable low-temperature phase with a rhombic lattice up to 105 "C, a high-temperature phase with a hexagonal lattice [1, 21 above this temperature, and a cubic modification of the compositon Chl.&3 above 480 O C resembling Cues, [3].C h S is a p-conducting material both in thin and massive specimens. Elsewhere the electric conductivity a, the thermo-e.m.f. u, the Hall effect, and the heat capacity of polycrystalline C b S have been measured between 20 and 600 OC. T w o anomalies due t o phase transformations have been found in these parameters. If there is a deficiency of sulphur the electric conductivity of CU$ decreases. I n the case of stoichiometry the activation energy for impurities amounts to 0.062 eV, the concentration of holes is 2.4 x 1010 ~r n -~, and the mobility is equal to 12 cm2/Vs [4, 51.Depending on disturbances of the stoichiometry thin layers of Cuss with nand p-type conductivity have been obtained by vacuum evaporation [7].Investigations on the transfer phenomenon in thin and massive specimens of polycrystalline Cu2S have been carried out [8], but no anomalies in Q and a have been found at the transition point from the rhombic modification to the hexagonal one. There is also a discrepancy between the values for the parameters obtained by different workers [4, 6, S, and 111.5 Phvica 28/1

Promising and Eco‐Friendly Cu2X‐Based Thermoelectric Materials: Progress and Applications

“…This should be attributed to the band flattening with increasing the superionicity and level of Cu disorder . Similar change in m * has also been observed in Cu 2 S when Cu 2 S transfers from low‐superionicity cha‐rt phase into partial‐superionic cha‐ht phase (Figure b) …”

“…[191] Similar change in m* has also been observed in Cu 2 S when Cu 2 S transfers from lowsuperionicity cha-rt phase into partial-superionic cha-ht phase (Figure 7b). [179,[193][194][195] Adv. Mater.…”

EPr study of copper(I) sulphide

“…high-frequency method (9.3 GHz), while the measurements in [4] are based on a static method. Above 403 K we did not detect, within the experimental error, any changes in the EPR line intensity and this fact is consistent with the data of[4]. As…”

Are Binary Copper Sulfides/Selenides Really New and Promising Thermoelectric Materials?

“…Scientists in eastern Europe apparently started to study the TE properties of Cu 2 S in the middle of the 1960s . Abdullaev et al reported Seebeck coefficients ( S ) between 100 and 200 μV K −1 in the α phase, about 300 μV K −1 in the β phase, and up to 960 μV K −1 in the γ phase (at 670 °C) . As far as resistivity ( ρ ) is concerned, the values measured by this team were about 2 mΩ cm for both the α and the β phase.…”