Suppression of Rotational Twins in Epitaxial B₁₂P₂ on 4H-SiC

Abstract

B12P2 was grown epitaxially on (0001) 4H-SiC using two different substrate miscuts: a standard 4° miscut toward the [112̅0] and a custom miscut 4° toward the [11̅00]. Epitaxy on substrates miscut to the [112̅0] resulted in highly twinned B12P2 films with a rotational twin density of approximately 70% twin orientation I and 30% twin orientation II. In contrast, epitaxy on substrates tilted toward the [11̅00] produced films of >99% twin orientation I. A H2 etch model is used to explain the 4H-SiC surface morphology for each miscut prior to epitaxy and demonstrate how the surface steps influence the nucleation of B12P2 twin orientations. Surface steps on substrates miscut to the [112̅0] tend to be zig-zagged with steps rotated 60° from one another producing B12P2 crystals that nucleate in orientations rotated by 60°, hence forming rotationally twinned films. Steps on substrates tilted to the [11̅00] tend to be parallel resulting in crystallographically aligned B12P2 nucleation.

Substrate-mediated growth of oriented, vertically aligned MoS2 nanosheets on vicinal and on-axis SiC substrates

“…If the step orientation were to play a dominant role, we would expect to see the majority of MoS2 flakes with the same orientation due to the reduced symmetry of the vicinal surface, as has been recently demonstrated for h-BN grown on vicinal Cu(110) [19,20]. Alternatively, the existence of three MoS2 orientations on the surface may be indicative that the surface of the vicinal substrate initially possess jagged step edges, as opposed to parallel, singly oriented steps, or the growth process induces jaggedness in the steps [41]. We note that the precise morphology of the 4H-SiC surfaces could not be verified by AFM, although the increased step density of the vicinal surface compared to the on-axis surface is evident in Figure S5 (Supporting Information).…”

Texture evolution in rhombohedral boron carbide films grown on 4H-SiC(𝟎𝟎𝟎𝟏̅) and 4H-SiC(0001) substrates by chemical vapor deposition

“…In comparison to structurally similar materials such as rhombohedral boron subphosphide (B12P2) and subarsenide (B12As2), the threshold temperature for epitaxial growth for r-BxC is comparable to the one reported for the CVD of B12P2 17 and similar structural variants such as twinning was observed in B12As2 [18][19][20] and B12P2 17 epitaxy, albeit on on-axis Si-face 4H-SiC(0001). A notable difference is observed in the evolution of crystalline quality with temperatures as seen from rocking curves measurements: the crystalline quality of B12P2 and B12As2 was reported to degrade from 1350°C 21 and 1450 °C19 , respectively, while the crystalline quality of r-BxC continues improving even up to 1500 °C. This could be attributed to the formation of volatile P or PHx (respectively As or AsHx) species from the deposited film, which is less prone to occur in the case of carbon, albeit at the cost of forming graphite.…”

Texture evolution in rhombohedral boron carbide films grown on 4H-SiC(0001̄) and 4H-SiC(0001) substrates by chemical vapor deposition

“…A notable difference is observed in the evolution of crystalline quality with temperature as seen from rocking curves measurements: the crystalline quality of B 12 P 2 and B 12 As 2 was reported to degrade from 1350 °C (ref. 21) and 1450 °C, 19 respectively, while the crystalline quality of r-B x C continues improving even up to 1500 °C. This could be attributed to the formation of volatile P or PH x (respectively As or AsH x ) species from the deposited film, which is less prone to occur in the case of carbon, albeit at the cost of forming graphite.…”