Comparative Study of Boron Precursors for Chemical Vapor-Phase Deposition-Grown Hexagonal Boron Nitride Thin Films

Two different boron precursors, diborane (B2H6) and trimethyl boron ((CH3)(3)B, TMB), are investigated for chemical vapor-phase deposition (CVD)-grown hexagonal boron nitride (h-BN) on alpha-Al2O3(0001) substrates. The BN layer grown using TMB includes a large amount (2 x 10(20) cm(-3)) of carbon atoms, which is 60 times higher than that in the BN layer grown using B2H6. The X-ray diffraction 2 theta/omega scans for BN film grown using B(2)H(6)exhibit theh-BN (002) peak. The BN film obtained using TMB includes turbostratic BN (t-BN). The E(2g)Raman peak frequencies in B(2)H(6)and TMBh-BN are observed at 1368.8 and 1369.7 cm(-1), respectively. The Raman peak shift to a higher frequency indicates that a larger compressive strain is induced using TMB than using B2H6. The full width at half maximum of the B(2)H(6)and TMB Raman peak frequencies is 21.8 and 42.7 cm(-1), respectively. The cathodoluminescence spectra of B(2)H(6)h-BN show the band-edge emissions at 225 and 232 nm, whereas only a 300 nm broadband is obtained in TMBh-BN. It is suggested that the carbon atoms in TMB prevent the formation of highly crystallineh-BN thin films.

Automated summary

Two different boron precursors, diborane and trimethyl boron, were investigated for h-BN growth, with the BN layer grown using TMB containing a higher amount of carbon atoms and exhibiting turbostratic BN structure compared to that grown using B2H6. The Raman peak frequencies and widths indicate that TMB induces a larger compressive strain and prevents the formation of highly crystalline h-BN thin films.