Fabrication of nanopatterns on H-passivated Si surface by AFM local anodic oxidation

Fabrication of nanopatterns on H-passivated Si surface by AFM local anodic oxidation

Mo, Yufei, Wang, Ying, Bai, Mingwu. Fabrication of nanopatterns on H-passivated Si surface by AFM local anodic oxidation. Physica E, Vol. 41. 2008. pp. 146-149.

Joshua D. Swartz

Purpose of Study

To develop nano-sized patterns from localized electrochemical oxidation (local anodic oxidation, LAO) of a H-passivated Si surface with atomic force microscopy (AFM).

Methods

Atomic force microscopy (AFM) was used in contact mode with a silicon cantilever with an electrically conductive tip coated by platinum. The tip is conic with a radius smaller than 25 nm. With the humidity (15-80%) and the temperature (10^oC) controlled, oxides were allowed to grow on a chemically reactive substrate (H-passivated Si) by the application of a pulse bias voltage between the conductive tip and the sample surface, which serves as an anode. Water is present between the tip and surface, providing the oxygen needed for the reaction to occur. This method is called local anodic oxidation (LAO) because oxidation only occurs where the anode makes contact with the surface.

Key Findings

1. The LAO process is controlled by pulsed bias voltage, pulsewidth, and humidity.

2. The tallest silica pillars (1.3 nm) were developed under the highest tip-sample pulse voltage (10 V) and longest pulsewidth (100 ms).

3. There is a linear dependence between the sample height and the tip-sample pulse bias voltage and pulsewidth.

4. An increase in humidity (from 10-85%) showed a linear increase in silica height.

Definitions

Local anodic oxidation (LAO): Oxidation caused by a voltage differential between a small tip and a surface.

H-passivated surface: To clean a surface of silica by introducing H to the surface, preventing non-specific oxidation of the surface.