Fabrication of Al2O3/Al structure by nitric acid oxidation at room temperature

Abstract

Abstract:A thick Al 2 O 3 /aluminum (Al) structure has been fabricated by oxidation of Al with 68wt% and 98wt% nitric acid (HNO 3 ) aqueous solutions at room temperature. Measurements of the Al 2 O 3 thickness vs. the oxidation time show that reaction and diffusion are the rate-determining steps for oxidation with 68wt% and 98wt% HNO 3 solutions, respectively. Observation of transmission electron micrographs shows that the Al 2 O 3 layer formed with 68wt% HNO 3 has a structure with cylindrically shaped pores vertically aligned from the Al 2 O 3 surface to the Al 2 O 3 /Al interface. Due to the porous structure, diffusion of HNO 3 proceeds easily, resulting in the reaction-limited oxidation mechanism. In this case, the Al 2 O 3 /Al structure is considerably rough. The Al 2 O 3 layer formed with 98wt% HNO 3 solutions, on the other hand, possesses a denser structure without pores, and the Al 2 O 3 /Al interface is much smoother, but the thickness of the Al 2 O 3 layer formed on crystalline Al regions is much smaller than that on amorphous Al regions. Due to the relatively uniform Al 2 O 3 thickness, the leakage current density flowing through the Al 2 O 3 layer formed with 68wt% HNO 3 is lower than that formed with 98wt% HNO 3 . PACS

Fabrication and design rules of three dimensional pyrolytic carbon suspended microstructures

“…Example wet etching processes are silicon dioxide (SiO 2 etching with hydrofluoric acid (HF) (Equation 2.1), chromium (Cr) etching with ceric ammonium nitrate (NH 4 ) 2 Ce(NO 3 ) 6 (Equation 2.2) with perchloric acid (HClO 4 ) as an optional additive and aluminum (Al) etching with phosphoric acid/nitric acid mixture H 3 PO 4 /HNO 3 (Equation 2.3) [59].…”