Study of large magnetoresistance of thin polycrystalline Bi films annealed at critical temperatures

Abstract

This paper reports an investigation of the large magnetoresistance (MR) of 0.3 -1.5 µm thick polycrystalline Bi films deposited in vacuum on non-crystalline substrates and annealed at critical temperatures. The occurrence of critical temperatures is associated with intensive growth of crystallites. It is demonstrated that such films consist of large 50 -200 µm high-quality crystallites and exhibit a large transverse MR. At temperatures higher than 77 K the magnitude of the MR can exceed that of epitaxial Bi films. The experimental results are interpreted on the basis of a polycrystalline Bi thin-film model. The data suggest that in Te-doped Bi films the MR can be larger than that in pure Bi films. It is found that the grainboundary scattering is weak. However, there exist rather isotropic extra carrier scattering channels which reduce the anisotropy of electrical conductivity and MR. The relative importance of this extra scattering changes with temperature.

Longitudinal magnetoresistance of uniaxially deformed thin polycrystalline Bi films

“…The good fits between the experimental and calculated values of MR was obtained using an additional scalar relaxation time, which reduced the L-electron and T -hole mobilities by 30%. This could be explained by assuming that rather isotropic extra scattering channels exist, such as scattering from the film surface or from other imperfections [9]. On the other hand, there is a difference between the experimental and calculated MR values for the strained and compressed Bi films.…”

“…High quality single-crystal (epitaxial) Bi films exhibit large magnetoresistance (MR) effects at low and room temperatures [5,7,8]. Only very recently high quality Bi thin films have been produced using the method of evaporation of Bi onto a non-crystalline dielectric substrate in high vacuum with a post-annealing process at critical temperatures T c close to the film melting temperature [9,10]. The large magnetoressistance of such films is associated with high anisotropy of L-electron mobility in large high quality crystallites.…”

Transverse magnetoresistance of uniaxially deformed thin polycrystallinen- Bi films

“…The films were plated at substrate temperature 390 K. The film thickness d varied from 0.3 to 1.5 µm. The annealing process was performed in vacuum at critical temperature T A near the film melting temperature [10,11]. At this temperature small molten crystallites create favourable conditions for the growth of larger crystallites having a higher quality and more ordered crystalline structure.…”

“…High-quality single-crystal (epitaxial) Bi films exhibit large magnetoresistance (MR) at low and room temperatures [7][8][9]. However, the fabrication of such films is expensive and complicated because special techniques such as molecular beam epitaxy (MBE) growth [9], or electrolytic deposition (electrodeposition) on orientated single-crystal substrates combined with special annealing [6,8] produced using an inexpensive and useful method of the evaporation of Bi onto various non-crystalline dielectric substrates in high vacuum with a postannealing process at critical temperatures close to the film melting temperature [10,11]. The large magnetoresistance of these films is associated with high anisotropy of L-electron mobility in large high-quality crystallites.…”

Nucleation and Growth of Bismuth Electrodeposition from Alkaline Electrolyte

“…Bi has been attracted many interests from physicists and chemists because of its unique physical and chemical properties. Owing to its large magnetoresistance, [1][2][3][4][5] thermoelectric efficiency 6 and interesting quantum effects, 7 Bi films possessed many applications in electrochromic devices, environmental detection, catalysis, superconductivity, thermoelectric, and piezoelectric. [8][9][10][11][12][13] In recent years, electrodeposition is the least expensive, effective, and readily adoptable method to deposit Bi films.…”