Structural study of bismuth films and its consequences on their electrical properties

Abstract

2014 Les auteurs étudient les propriétés structurales des couches minces de bismuth à 1'aide des techniques suivantes : diffraction des électrons par réftexion, diffraction des rayons X, microscopie électronique par balayage et diffraction et microscopie électronique par transmission. Ils rappellent les propriétés électriques des couches minces de bismuth (mesures de conductivité et du facteur RH). Il apparait que les états de surface jouent un rôle déterminant dans les définitions des propriétés du facteur RH et de la conductivité. Cette conclusion est étayée par les résultats de 1'etude structurale. Une propriété importante du mécanisme de conduction telle que le libre parcours moyen des porteurs a été estimée et sa valeur est aussi en accord avec les résultats de l'étude structurale.La densité des états de surface ainsi que la hauteur de barrière associée aux joints de grain ont été évaluées en fonction des différentes techniques de preparation. Abstract. 2014 The structure of bismuth thin films prepared according to three different deposition techniques is inspected by : reflection electron diffraction, X-ray diffraction, scanning electron microscopy, transmission microscopy and electron diffraction. The electrical conduction properties, RH and conductance measurements, of these films are then discussed. It appears that surface states play a major role in dictating the properties of both RH and conductivity. This is clearly confirmed with the aid of the conclusions of the structural study. By comparing size effect theories with the conductivity data the carrier mean free path can be estimated to be of the order of 1 000 Å in good agreement with the observation of the film structure. The surface state density and the energy barrier that controls the carrier transport across the grain boundaries have also been evaluated as a function of the preparation technique.

Enhancement of Thermoelectric Performance of Ball‐Milled Bismuth Due to Spark‐Plasma‐Sintering‐Induced Interface Modifications

“…As a result, the PF enhancement and hence higher ZT was observed in the sample ball‐milled in inert atmosphere (Bi‐bm60‐inert (Ar) atm) as compared to those ball‐milled in ambient atmospheric conditions (Bi‐bm60‐atm) with same SPS conditions. This is consistent with the previous reports depicting the effect of preparation conditions on surface transport in Bi thin films,28 and hence our results further confirm surface modifications as the most probable cause for observed enhancement in TE properties.…”

Geometries for high spatial resolution Hall probes

“…Thus the change of sign in the Hall coefficient of Bi probes is not surprising and indeed has been noticed earlier by several authors [12,13,14,15,16].…”

Bi0.99Sb0.01 Thin Film Transport Properties and Size Effect

“…and V = (D/λ os )[ln(1/p -)] (11) where D is the grain diameter that it determined from x-ray (D=87.31 nm and d=120 nm). U and V were calculated and are listed in Table (2) with the other available data for comparison.…”

“…Bi-Sb is an efficient thermoelectric material at low temperature [3,4,6].The constituents of Bi 0.99 Sb 0.01 thin films have been the subject of many studies since it is regarded as one of the constituent materials of many binary and ternary compounds used in electronic devices. Previous studies [7][8][9][10][11][12] revealed that Bi-Sb thin film form crystallized in the hexagonal system and they also found that, the mean grain size increased with increasing the film thickness and decreased with Sb content. Many studies [7,[12][13][14][15][16] revealed that with decreasing film thickness, the resistance increases regularly, though as the thickness reaches certain magnitude, ρ starts to drop manifesting an anomalous size effect.…”