Fig. 4: Imaging and scattering from steps.
From: In situ microbeam surface X-ray scattering reveals alternating step kinetics during crystal growth
a AFM image of steps of height c/2 (2.6 Å) on the vicinal GaN substrate used in X-ray measurements. To emphasize the positions of steps, we plot the amplitude error signal, which is proportional to the height gradient in the scan direction (y). Image was obtained ex situ at room T after an anneal for 300 s at 1118 K in zero-growth conditions (0% H2, 0 TEGa). Average fraction over a 2 × 2 μm2 area of terrace family marked black at top is 0.47. The average double-step spacing of w = 573 Å corresponds to a miscut angle of \({\tan }^{-1}(c/w)=0.5{2}^{\circ }\). b Profile of split CTRs from the vicinal surface, measured at T = 1170 K during growth at 0.053 μmol min−1 TEGa and 50% H2. The splitting of the CTRs ΔQy = 0.0110 Å−1 corresponds to a miscut angle of \({\tan }^{-1}[{{\Delta }}{Q}_{y}/(2\pi /c)]=0.5{2}^{\circ }\), in agreement with the AFM result.
