Investigation of optical and structural properties of ceramic boron nitride by terahertz time-domain spectroscopy

Abstract

Six types of hexagonal boron nitride are investigated by terahertz time-domain spectroscopy. The loss coefficient is shown to be linear with porosity, while variations in refractive index indicate the distribution of porosity within the structure. Pyrolytic boron nitride is demonstrated to be suitable as a terahertz optical material.

Dielectric Properties of Boron Nitride in THz Region Synthesized with Nonenergetic CVD

“…8b), which showed very low absorption behavior of BN in the range 0.2-3.0 THz, for example, at 2.0 THz the mean value is 56 AE 12 cm. 24 With respect to these results, the absorption coefficient revealed similar slowly growing tendency in the investigated THz region. 24 With respect to these results, the absorption coefficient revealed similar slowly growing tendency in the investigated THz region.…”

“…The variation of the refractive indices found by these authors is in the same range as was found in our study, however, the variations were attributed also to the changes in the porosity of the investigated samples. Distinct detection of the differences in refractive indexes related to the birefringence of pBN 23,24 reported in the literature could be responsible for these variations. Distinct detection of the differences in refractive indexes related to the birefringence of pBN 23,24 reported in the literature could be responsible for these variations.…”

“…It has very good thermal conductivity and optical transparency, high chemical stability against oxidation even at increased temperatures (up to 1800°C), and hence it is suitable as a hard layer coating material. 23,24 In this study, we have investigated the experimental conditions for the synthesis of pBN by nonenergetic chemical vapor deposition as a simple production route for some technical applications. [9][10][11][12][13][14] High pressure high temperature (HPHT) synthesis is used to synthesize bulk cBN from hBN in the presence of a suitable catalyst, while energetic chemical vapor deposition and ion-beamand/or plasma-assisted deposition are used to produce thin layers of cBN coatings.…”

Terahertz characterization of electronic components and comparison of terahertz imaging with x-ray imaging techniques

“…Using Equation(2) and Equations(3), refractive indices and attenuation coefficients of the counterfeit ICs ofFigure 3are calculated as 1.82 and 2.475×10 4 dB/cm respectively. The calculated refractive indices are in the reported range of refractive indices for ceramics16 . This confirms the validity of the experiment.b) THz techniques in reflection modeThe different layers of a given component are extracted by using reflection mode THz measurement.…”

“…Variations of refractive indices of materials in different THz frequencies can give a signature to characterize them 16,17 . In Figure 7 refractive indices of two authentic ICs and their counterfeit one are depicted.…”