In situ infrared and visible-light ellipsometric investigations of boron nitride thin films at elevated temperatures (original) (raw)
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In situ infrared ͑IR͒ spectroscopy and visible-light ͑VIS͒ spectroscopic ellipsometry over the spectral range from 700 to 2000 cm Ϫ1 and 1.5-3.5 eV, respectively, were used to investigate the optical behavior of boron nitride ͑BN͒ thin films at temperatures from room temperature ͑RT͒ to 600°C. The polycrystalline hexagonal ͑h͒ and mixed-phase h-and cubic (c)-BN thin films were deposited by magnetron sputtering on ͓001͔ silicon. We observe a reversible moisture incorporation process in as-grown h-BN samples. When stored in normal ambient, the h-BN thin films absorb water into thin-film micropores. When annealed in ultrahigh vacuum or a dry nitrogen atmosphere, the samples expel moisture but retain their microstructure. This is observable by reduction of the thin-film refractive indices in accordance with changes in the IR lattice resonance behavior. The optical properties of high c-BN content thin films remain unchanged during annealing. And both intrinsic h-and c-BN thin-film VIS refractive indices are nearly temperature independent, at least up to 600°C. Therefore, RT BN optical constants can be used for feedback loop control in in situ thin-film growth at temperatures up to 600°C. ͓S0021-8979͑98͒07613-0͔ a͒ Electronic
Optical properties of boron nitride thin films
Diamond and Related Materials, 1994
Boron nitride thin films were deposited onto crystalline silicon and alkali halide substrates by plasma-enhanced chemical vapour deposition of BF~, Ne, H e and Ar gas mixtures. Films were prepared on both powered and grounded electrodes of the capacitatively coupled system. The deposits were analysed by ellipsometry, Fourier transform IR spectroscopy and UV spectroscopy to determine their optical properties. The relative composition was determined using nuclear reactions induced by 1 MeV deuteron bombardment and Auger spectroscopy. Ion bombardment during growth was found to affect the optical properties of the material, since fihns prepared with low flows of argon and those placed on the live electrode have smaller refractive indices, larger I R absorption peaks for lhe cubic phase, and wider optical gaps.
Optical and structural characterization of boron nitride thin films
Diamond and Related Materials, 1995
Thin films of boron nitride were prepared by three deposition methods: r.f. plasma deposition, pulsed laser deposition and r.f. magnetron sputtering. The films were characterized by Fourier transform IR spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, optical transmittance spectrophotometry and spectroscopic ellipsometry in the visible-near-UV range. The films are highly transparent with atomic B:N ratios from 2.5 to 1.1, and refractive index values between 1.6 and 1.9 depending on deposition conditions. IR and Raman spectra revealed a short-range atomic order with hexagonal BN bonds, which is more marked in r.f. plasma-deposited films. From the spectroscopic ellipsometric measurements, the optical response of the films was analysed using a two-layer model and applying the Bruggeman effective medium approximation for each layer.
Thin Solid Films, 1998
. We focus on the application of infrared spectroscopic ellipsometry IRSE to simultaneously determine phase and Ž . microstructure of mixed-phase thin films such as polymorphic-polycrystalline boron nitride BN thin films deposited by Ž . magnetron sputtering on 100 silicon. We discuss a recently presented microstructure-dependent model for infrared optical properties of mixed-phase thin films which contain anisotropic materials. In particular, the IRSE data are sensitive to the pure Ž . Ž . or mixed hexagonal h and cubic c BN thin film layer structure, phase composition and average grain c-axis distribution of the hexagonal phase. ᮊ 1998 Elsevier Science S.A.
Synthesis and structural characterization of boron nitride thin films
The purpose of this paper is to present first results of an investigation on the properties of boron-nitrogen thin films obtained by different deposition techniques. Films of different stoichiometries were produced on silicon substrates using r.f. magnetron sputtering and ion-beam-assisted deposition.
Spectroscopic ellipsometric study of boron nitride thin films
Diamond and Related Materials, 1996
Thin films of boron nitride (BN) have the following interesting properties as a promising alternative to diamond in optical, electronic and mechanical applications: mechanical hardness (c-BN), low density, chemical inertness, high optical transparency, high thermal conductivity and high electrical resistivity. However, these attractive properties depend strongly on the deposition conditions.
Humidity effects on the electrical properties of hexagonal boron nitride thin films
Elsevier, Thin Solid Films, 2004
Thin films of hexagonal boron nitride (h-BN) were grown by a plasma enhanced chemical vapour deposition (PECVD) technique. The quality of the films was assessed by infrared spectroscopy, microRaman spectroscopy as a function of annealing temperature and by X-ray photoelectron spectroscopy. The films proved to be thermally stable up to 1370 K. Current-voltage measurements were performed, as a function of humidity, using metal-insulator-semiconductor and metal-insulator-metal structures. Typical resistivities were found in the range 10 13 -10 14 V cm in dry air and exhibit high sensitivity against humidity. The influence of the mean orientation of the c-axis of the BN films was considered. Sawtooth voltage pulse trains were also applied. Threshold switching phenomena were observed, but only in atmosphere containing humidity. The values of the switching voltages depend strongly on the relative humidity (RH), on the characteristics of the applied sawtooth voltage pulse trains, as well as on the nature of the metallic electrode. D
Applied Physics Letters, 1996
Boron nitride ͑BN͒ thin films ͑containing mixed cBN/hBN phase͒ have been deposited on Si͑100͒ substrates using neutralized nitrogen beam and electron beam evaporation of boron. All as-deposited BN films were p type with a room-temperature carrier concentration in the range of 5ϫ10 16 to 1ϫ10 17 cm Ϫ3 . The Mg-doped BN films showed carrier concentrations in the range of 1.2 ϫ10 18 cm Ϫ3 to 5.2ϫ10 18 cm Ϫ3 when the Mg cell temperature was varied from 250 to 500°C. The films were analyzed for both majority elements ͑B and N͒ and dopant/impurity ͑Si, Mg, Fe, etc.͒ incorporation using secondary ion mass spectroscopy and mass spectroscopy of recoiled ions ͑MRSI͒. MRSI is shown to be superior for dopant characterization of boron nitride thin films.