Nanodiamond in a 2–5-nm size interval (which is typical for an appearance of quantum confinement effect) show Raman spectra composed of 3 bands at 1325, 1600, and 1500 cm−1 (at the 458-nm laser excitation) which shifts to 1630 cm−1 at the 257-nm laser excitation. Contrary to sp2-bonded carbon, relative intensities of the bands do not depend on the 458- and 257-nm excitation wavelengths, and a halfwidth and the intensity of the 1600 cm−1 band does not change visibly under pressure at least up to 50 GPa. Bulk modulus of the 2–5-nm nanodiamond determined from the high-pressure study is around 560 GPa. Studied 2–5-nm nanodiamond was purified from contamination layers and dispersed in Si or NaCl.
First, the Al/AlN/Al/Cr/diamond single crystal piezoelectric layered structure has been developed, and its properties have been investigated up to 8 GHz. The peculiarities associated with the influence of piezoelectric film on the Q factor of high overtones of substrate have been pointed out. High Q ∼ 104 has been found at 6–7 GHz band.
New bulk nanocomposite thermoelectric materials composed from nanocrystallites of Bi–Sb–Te alloys covered by C60 molecules have been synthesized and studied. The fullerene molecules provide thermal phonons blocking and particular charge transfer in the nanocomposite. The molecules act as electron traps, and thus decrease the density of free electrons in n‐type semiconductor and generate holes in p‐type materials. The capture of electrons is not accompanied by shifts of the Raman bands in C60 spectra. The density of free charge carriers and their Hall mobility change nonmonotonically with the increase of fullerene content in Bi–Sb–Te–C60 nanocomposites. The maximum value of thermoelectric figure of merit ZT = 1.15 was obtained in p‐type nanocomposite that is 30% higher than in the undoped starting material. The observed phenomenon provides new ways for transport properties optimization of thermoelectric materials and thermoelectric devices efficiency increase.
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