Temperature Dependence of Raman Scattering in 4H-SiC Films under Different Growth Conditions

Abstract

The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550 K. The effects of growth conditions on E2(TO), E1(TO) and A1(LO) phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2(TO) modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2(TO) mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 (longitudinal optical plasma coupling (LOPC)) mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1(LOPC) mode in 4H-SiC.

Aligned MoO2/MoS2 and MoO2/MoTe2 Freestanding Core/Shell Nanoplates Driven by Surface Interactions

“…Additionally, annealing the substrates prior to CVD leads to increased nucleation and alignment. At high temperatures, SiC(0001) undergoes a range of surface reconstructions that depend on temperature, pressure, and environmental composition. − Figure c shows a SEM image of a SiC sample that was annealed at 1000 °C under Ar prior to growing the MoO 2 /MoS 2 nanoplates, resulting in ∼3× more plates on the surface. This increase in nucleation indicates that substrate surface chemistry is playing an influential role in particle nucleation.…”

Strong Coupling of Folded Phonons with Plasmons in 6H-SiC Micro/Nanocrystals

“…The Raman spectra of the 6H-SiC films with a mean size of 1.25 μm and four different thicknesses are displayed in Figure 3 a, in which two Raman spectra of the 6H-SiC films with a mean size of 0.55 μm and thicknesses of 1.5 and 3.6 μm are shown for comparison. With regard to the 0.5 μm thick SiC film, the peaks at 795.5, 786.5, and 765.0 cm −1 are assigned to the FTO modes at x = 0, 1/3, and 1 ( Figure 3 b) [ 27 , 28 , 29 ]. There is a new peak at 776.0 cm −1 between the x = 1/3 and 1 FTO modes, which can be assigned to the x = 2/3 FTO mode.…”