Growth of ultrathin Al2O3 islands on hBN particles by atomic layer deposition in a custom fluidized bed reactor using Al(CH3)3 and H2O

Hexagonal boron nitride (hBN) powder is widely used in industry because of its unique physical and chemical properties. Atomic layer deposition (ALD) allows the growth of such ultrathin coatings. This technique is performed in a fluidized bed reactor (FBR) using trimethylaluminum (TMA) and H2O as precursors under atmospheric pressure. In this study, the homemade heat-resistant stainless steel fluidized bed was designed and constructed as a vertical, circular cross-section column for conducting the thermal ALD process. Al2O3 growth mechanism is challenging and depends on surface properties. After the ALD process, island growth mode was observed. The deposition of ultrathin alumina islands was successfully obtained on hBN. Growth per cycle (GPC) values were calculated between 0.03-0.1 nm/cycle based on TEM imaging. The thickness growth rate (TGR) of a (mean) value was increased from 1.07 nm at 10 cycles to 1.49 nm at 50 cycles, and b (mean) value was increased from 5.67 nm at 10 cycles to 10.9 nm at 50 cycles. With increasing number of cycles, the growth of the island can reach the highest values both vertically and horizontally according to the schematic depicting a hemisphere-shaped island form model. We found a non-linear growth according to substrate-inhibited growth.