Oscillatory behaviour of resistivity with thickness in bismuth thin films

Lattice distortion energy spectra of as-grown bismuth thin films and their thickness dependence

Abstract: Bismuth thin films of various thicknesses between 15 nm and 350 nm were vacuum deposited at room temperature on to glass substrates, immediately after which they were twice heat treated at a uniform rate. During the heat treatment, the resistance changes were monitored and, using these data, the initial lattice distortion energy spectra of as-grown bismuth thin films have been evaluated. It is found that the defects have preferential activation energy values around 1.06 eV, 1.14 eV and 1.32 ev. It is also found that ∫F0 (E) dE oscillates with thickness, which is attributed to the quantum size effect.

Morphological, Structural, and Compositional Characterization of Electrodeposited Bi(1-x)Sb(x) Nanowires

Abstract: Bi$_{1-x}$Sb$_x$ nanowires with controlled diameter ($20$ to $200$,nm) and composition over a wide range from $x = 0$ to $05$ and $x=1$ were fabricated by electrochemical deposition in etched ion-track templates These nanowires are interesting for the investigation of the influence of quantum-size effects on the thermoelectric efficiency The influence of the electrolyte and the deposition potential on the electrochemical deposition of Bi$_{1-x}$Sb$_x$ nanowires in polymer templates made of polycarbonate (PC) and poly(ethylene terephthalate) (PET) was investigated Composition, crystalline orientation, and crystallite size of the nanowires were measured using X-ray diffraction and scanning and transmission electron microscopy It was demonstrated that the composition of the nanowires can be adjusted by the concentrations of bismuth and antimony in the electrolyte and the deposition potential Nanowires grown in PET exhibited a pronounced surface roughness compared to the nanowires deposited in PC and offer a novel possibility for the structuring of the nanowire surface to increase the thermoelectrical efficiency by enhanced phonon surface scattering Seebeck coefficient and temperature dependence of the resistance of nanowire arrays were measured in a cryostat for temperatures down to $sim 30$,K The absolute value of the Seebeck coefficient decreased with decreasing temperature and was lower than the value of the respective bulk material

Variation of energy gap and resistivity minimum position with thickness in bismuth thin films

Abstract: Bismuth thin films of different thicknesses between about 20 and 225 nm are vacuum deposited at room temperature in a vacuum of 3 × 10−3 Pa. The films are heat-treated “in situ” and the resistances monitored. It is found that the resistivity-temperature plots of the films after heat-treatment are non-linear and exhibit a minimum whose position is a function of thickness. It is also found that the films behave as semiconductors, the band gap decreasing with increasing thickness. The observations are interpreted on the basis of quantum size effect and the limitation of the electronic mean free path by the grain size of the films. Dunne Wismuth-Schichten verschiedener Dicken zwischen 20 und 225 nm werden bei Zimmer-temperatur im Vakuum von 3 × 10−3 Pa hergestellt. Die Schichten werden “in situ” getempert und der Widerstand verfolgt. Es wird gefunden, das die Widerstands-Temperatur-Verlaufe der Schichten nach der Warmebehandlung nichtlinear sind und ein Minimum aufweisen, dessen Lage von der Schichtdicke abhangt. Es wird ebenfalls gefunden, das sich die Schichten wie Halbleiter verhalten, wobei die Bandlucke mit zunehmender Schichtdicke abnimmt. Die Beobachtungen werden auf der Grundlage des Quantensize-Effekts und der Begrenzung der mittleren freien Weglange der Elektronen durch die Korngrose der Schichten erklart.

Manifestations of the quantum size effect in the electrochemical behaviour of thin bismuth films

Abstract: The photoemission current (j) and the differential capacitance of the double layer (C) on 20-200 nm thick bismuth films have been measured. The current j as a function of potential (E) follows the 5/2 law for films of thickness exceeding 80 nm and for bulk bismuth. The current j as a function of E for thin films exhibits steps whose width increases as the thickness decreases. The absolute values of j and C also decrease for thinner films. These effects are manifestations of the quantum size effect in the energy spectrum of charge carriers in bismuth. Estimations of the degree of metallization of the bismuth surface are presented.

Annealing and thickness effects on the electrical resistance of vacuum-deposited tin antimonide alloy films

Abstract: Tin antimonide alloy films, vacuum-deposited at room temperature onto glass substrates, were heated to a maximum temperature of about 300 °C and the changes in their electrical resistance with temperature were recorded. The initial lattice distortion energy spectra of the films have been determined from the resistance-temperature data. It is found that the F0(E)max and Emax values vary from 200×10-4 to 700×10-4ohms;cm/eV and from 1.55 to 1.74 eV respectively and that they depend upon the thickness of the film. The resistivities of the films due to thermal vibrations alone have been calculated and it is found that the calculated resistivity values for films of different thicknesses are in good agreement with the size effect theory.

Quantum size effect in thin Cd3As2 films

Abstract: An investigation has been carried out of the resistivity ϱ, Hall coefficient RH and Hall mobility μH as functions of film thickness for vacuum-evaporated thin Cd3As2 films. The films were evaporated in a vacuum of 10−5 torr onto mica substrates heated to a temperature ts of about 160 °C at a rate of deposition v of about 40 A s−1. The thicknesses of the films were in the range 0.02–0.2 μm. An oscillating character of the resistivity and the carrier mobility was observed for thicknesses of 0.03–0.1 μm. No distinct oscillations of the Hall coefficient were found. The analysis of the results obtained was performed on the basis of theories of the quantum size effect (QSE). The period of the oscillations measured from the experimental data was about 100 A, which is in good agreement with the calculated value of about 80 A.

Electrical resistivity of thin bismuth films

Abstract: For quantitative and reproducible observation of the quantum size effect (QSE) 78 samples of thin bismuth films were deposited at one time onto three muscovite substrates in ultrahigh vacuum. The electrical resistivity of these films, either in step-up series or a fixed thickness, was measured between 4.2 and 320 K. The experiments covered a thickness range from 300 to 3350 A. The measured resistivities had a large scatter among simultaneously deposited samples of a fixed thickness. This scatter became more pronounced with decreasing temperature and it was due to the variation of the TCR above liquid nitrogen temperature. The thickness dependence of the ratio of resistivities at 4.2 K and 77 K (ϱ4.2/ϱ77), which had a relatively small scatter, did not show the oscillatory behavior predicted by Sandomirskii.