Humidity effects on the electrical properties of hexagonal boron nitride thin films (original) (raw)
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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.
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
Journal of Applied Physics, 1998
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 hand 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 hand 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.
Scientific Reports, 2015
We report the studies of (1) the basic mechanism underlying the formation of defect-free, single crystalline boron nitride nanosheets (BNNSs) synthesized using pulsed laser plasma deposition (PLPD) technique, (2) the variation in the crystalline structure at the edges of the hexagonal boron nitride (h-BN) nanosheets and (3) the basic electrical properties related to the BNNSs tunneling effect and electrical breakdown voltage. The nanoscale morphologies of BNNSs are characterized using scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM). The results show that each sample consisted of a number of transparent BNNSs that partially overlapped one another. Varying the deposition duration yielded different thicknesses of sample but did not affect the morphology, structure and thickness of individual BNNSs pieces. Analysis of the SEM and HRTEM data revealed changes in the spatial period of the B3–N3 hexagonal structures and the interlayer distance...
Morphological Observation of Y and T Junctions in Nanostructured Boron Nitride Thin Films
Journal of Nanoscience and Nanotechnology, 2008
Formations of Y and T nano junctions have been observed in boron nitride films deposited on silicon substrates by plasma chemical reaction of diborane (B2H6 diluted in hydrogen) and ammonia (NH3) gases using dual frequency (microwave/radio) plasma enhanced chemical vapor deposition technique without any intentional heating of the substrates. It has been observed that these nano junctions form at a critical feed gas ratio of ammonia and diborane. We have investigated the effect of gas feed ratio R (=NH3/B2H6) in the plasma reaction chamber, keeping all other deposition parameters constant, on the morphology of boron nitride films. The deposited films are characterized by SEM, AFM, TEM and Laser Raman. For gas feed ratio, R < 100, octahedron and cubic morphologies have been observed in BN films and on increasing R to…
Influence of the nitrogen flow rate on the order and structure of PECVD boron nitride thin films
Journal of Non-Crystalline Solids, 2009
Three sets of boron nitride (BN) thin films are deposited with different N 2 /B 2 H 6 flow ratios (r = 4, 10 and 25) by plasma enhanced chemical vapor deposition (PECVD). The variations of physical properties in different deposition sets are analyzed by optical (XPS, FTIR, UV-visible spectroscopies), mechanical and electrical measurements. The films are considered to be deposited in a turbostratic phase (t-BN). Evolution of bonding configurations with increasing r is discussed. Relatively higher nitrogen flow rate in the source gas mixture results in lower deposition rates, whereas more ordered films, which tend to reach a unique virtual crystal of band gap 5.93 eV, are formed. Anisotropy in the film structure and film inhomogeneity along the PECVD electrode radial direction are investigated.
Role of Pressure in the Growth of Hexagonal Boron Nitride Thin Films from Ammonia-Borane
Chemistry of Materials, 2016
We analyze the optical, chemical, and electrical properties of chemical vapor deposition (CVD) grown hexagonal boron nitride (h-BN) using the precursor ammonia-borane (H3N-BH3) as a function of Ar/H2 background pressure (PTOT). Films grown at PTOT ≤ 2.0 Torr are uniform in thickness, highly crystalline, and consist solely of h-BN. At larger PTOT, with constant precursor flow, the growth rate increases, but the resulting h-BN is more amorphous, disordered, and sp 3 bonded. We attribute these changes in h-BN grown at high pressure to incomplete thermolysis of the H3N-BH3 precursor from a passivated Cu catalyst. A similar increase in h-BN growth rate and amorphization is observed even at low PTOT if the H3N-BH3 partial pressure is initially greater than the background pressure PTOT at the beginning of growth. h-BN growth using the H3N-BH3 precursor reproducibly can give large-area, crystalline h-BN thin films, provided that the total pressure is under 2.0 Torr and the precursor flux is well-controlled.
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.
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.