Extended Data Fig. 7: Interfacial quality of MEGA2D devices.
From: On-chip multi-degree-of-freedom control of two-dimensional materials
(a) AFM line scan of a clean h-BN flake on a Si pyramid. The average roughness is 0.11 nm over about 4 μm. (b) Large-scale AFM line scan of a Si pyramid, showing the parallelism between the Si pyramid (pink) and Si pillar surface (green). While the Si pillar has an increased roughness, the Si pyramid has the intrinsic roughness of a commercial Si wafer. (c-d) The optical image of (c) a normal MEGA2D device and (d) a defective MEGA2D device, taken through the fused silica substrate. The colours are saturated to show the colour variation. Defective devices typically show colour bands that indicate a tilt angle, whereas working devices do not show such bands. (e-f) Simulated colour (saturated) of an air gap (540 nm) between fused silica and silicon, (e) without tilt and (f) with a tilt of 0.01°. Colour variation can be seen on the upper-right corner of the Si pillar (circle). (g-h) Our MEMS actuators can be driven differentially to tilt the Si pillar/pyramid in either (g) y direction or (h) x direction, by an amount that is on the order of 0.008°. (i) Illustration of patterned h-BN for strain measurements. (j) Extracted strain profile along horizontal direction for a 45 nm thick h-BN flake on square pyramid (denoted by red dashed lines). The right panel shows the raw AFM image (amplitude channel). (k) Same measurements for a rounded pyramid and a 30 nm thick h-BN flake.
