Residual compressive stress induced infrared-absorption frequency shift of hexagonal boron nitride in cubic boron nitride films prepared by plasma-enhanced chemical vapor deposition

Abstract

The effects of compressive stress on the TO phonon frequencies of hexagonal boron nitride (hBN) in cubic BN (cBN) films were investigated using infrared absorption spectroscopy, showing that the B–N stretching vibration of hBN at 1380 cm−1 shifted to high wavenumbers under biaxial compressive stress with the rate 2.65 cm−1 per GPa, while the B–N–B bending vibration near 780 cm−1 shifted to low wavenumbers with the rate −3.45 cm−1/GPa. The density functional perturbation theoretical calculation was carried out to check the above phonon frequencies under stress for two typical orientations of hBN crystallite. The results are shown to be in fair agreement with the experimental data. Our results suggest that the residual compressive stress accumulated in cBN films can be evaluated from the IR peak position near 780 cm−1.

Residual compressive stress and intensity of infrared absorption of cubic BN films prepared by plasma enhanced chemical vapor deposition

“…Cubic BN thin films were deposited on Si wafers by lowpressure inductively coupled PECVD. [17][18][19] The plasma was generated at 1 mTorr with an input power of 7 kW, and the substrate bias was controlled by another radio-frequency (RF) power supply with an input power of 20-100 W. Before film deposition, the reactor chamber was pre-evacuated to a base pressure below 10 −7 Torr, then H 2 plasma and N 2 plasma were generated for 10 min and 30 min, respectively, to clean the substrate surface and chamber walls. Finally, the plasma gas composition was changed to Ar(20 sccm)+N 2 (0.3-1 sccm)+B 2 H 6 (0.03-0.1 sccm)+He(0.3-0.9 sccm) for film deposition.…”

“…The IR peak position was determined by fitting the spectrum with pure Lorentzian-type peak functions as described in Ref. [17]. The residual compressive stress was evaluated using the famous Stoney's equation, [11] where the substrate curvature was measured by a surface profilometer (KLA-Tenchor).…”

“…We once thought that this might be related to the density of states (DOS) of the TO phonon influenced by the residual stress. Early studies [14][15][16][17] have already shown that the peak position of phonon DOS varies with the strain (or stress). The experimental IR peak width is broadened more than the theoretical situation, suggesting that the strain is not uniform throughout the film.…”

Cross-sectional transmission electron microscopy studies of boron ion implantation in hexagonal boron nitride

“…Cubic BN is an important material because of its properties such as super hardness 75 GPa [6][7][8] high thermal stability for temperatures up to 2700°C, thermal conductivities of about 13 W/m K and low dielectric constant [9][10][11][12]. It is a better semiconductor as compared to diamond and other commonly used semiconductors such as Si and GaN including, wide indirect band gap of 6.5 eV, can be doped as a shallow p-type semiconductor with Be and Mg and as an n-type with Si and Zn [13,14].…”

Structures and Electromagnetic Properties of Boron Nitride Nanoribbons Doped with Transition Metals

“…[6][7][8] BN materials can form different polymorphs, such as the c-BN and w-BN consisting of sp 3 atoms, and the h-BN and r-BN with sp 2 atoms. [9] The h-BN-based materials, in particular, have been intensively studied owing to their extraordinary stability under normal conditions [10,11] and their role as an electrically-neutral model in understanding low-dimensional layered materials. [12] As a typical inorganic nonmetal compound composed of solely strong covalent BÀ N bonds, the h-BN nanosheet is also called 'white graphene' due to its ivory color, as distinguished from its structural analogue, the carbon graphene.…”