High Temperature Raman Scattering From Boron Nitride Coatings On Resistively Heated Graphite Surfaces

Abstract

Raman spectra of the hexagonal phase of boron nitride to temperatures exceeding 2000 °C. have been recorded using a pulsed -excitation gated -detection method. Surface temperatures were determined during rapid sample heating from analysis of corrected Stokes /anti-Stokes intensity ratios and from shifts in the resonance frequency of the 1366 cm-1 E9 mode. Successive spectra were acquired at time intervals as short as 33 msec corresponding to the pulse repetition frequency of the probe laser. Using this synchronous detection technique, the time evolution of graphite furnace temperatures was determined from measured spectra. Results indicate nearly complete rejection of sample blackbody radiation from the Raman scattered light at these high temperatures. A nearly linear relationship between the Eg resonance frequency and temperature was found. Phonon linewidths were also found to increase by a factor of three over this temperature range.

Thermomechanical Response of Supported Hexagonal Boron Nitride Sheets of Various Thicknesses

“…In contrast, the vdW forces suffice for the FL hBN to follow the substrate to a degree that depends on the hBN thickness. We note that the slope values measured for bulk domains are in moderate agreement with the values from Exarhos and Schaaf of ∼−0.028 56 and ∼−0.032 cm −1 /K, 57 respectively, for polycrystalline hBN, and are in good agreement with the recent work of Arutyunyan et al 58 of ∼−0.014 cm −1 /K, in the same temperature range.…”

<title>Transient stress evolution and crystallization in laser-irradiated amorphous titania sol-gel films</title>

“…The intensity ratio follows a Boltzrl_anndistribution fronn which a molecular temperature of the sample may be obta',ned. [13] \Vhile several experirner_tal difficulties must be addressed, this method allows temperatures to be determined in times asstnortas several nanose,conds. [14] The analytical rnethods described in the present work involve anal),sis of the Stokes Raman spectrum alone or the fiuorescer_ce response of a dopant located at the filrn-substrate interface.…”

Nanosecond time‐resolved Raman spectroscopy for solving some Raman problems such as luminescence or thermal emission

“…An alternative way to reduce the thermal emission, while minimizing the sample damaging, is to operate in the visible range but with a pulsed excitation laser coupled with the temporal filtering. This concept was first proposed by Exharos et al who performed Raman analysis of hexagonal boron nitride from room temperature up to 2000 °C using a pulsed 532 nm laser and time‐gated detection. This gated detection was also used for high pressure and temperature Raman measurements in diamond anvil cell .…”