Microcontact printing was used to form nanometer scale patterns of self-assembled monolayers (SAMs) on amorphous Si, crystalline Si, and SiO2 using octadecyltrichlorosilane (OTS) as the ink and an elastomer as the stamp. The patterns were subsequently transferred into crystalline Si substrates or amorphous Si films using the SAM of OTS as the resist film. Atomic force microscopy was used to characterize the quality of the SAM and the resulting patterns. Using a Si pillar structure as the master, “pancakes” of less than 80 nm in size were formed by over etching of the patterned OTS film on amorphous Si using KOH. The size of the resulting amorphous Si pancakes can be controlled by the etching time.

Writing of nanostructures on thin metal films using atomic force microscopy (AFM) was demonstrated. The writing experiments were done in a nitrogen ambient having variable humidity. Using a p-type heavily doped silicon AFM tip, a bias voltage was independently applied between the tip and the surface of a thin chromium layer deposited on a Si(100) substrate. Protruded patterns of various shapes were formed only on the water-adsorbed chromium surface when applying a negative bias on the tip. Their sizes were found to be dependent on the writing time, the bias voltage, and the humidity. The smallest feature size obtained is about 20 nm. From Auger electron spectroscopy (AES) analysis, the products are shown to be Cr oxides. The surface modification mechanism appears to be tip-induced local oxidation, i.e., anodization.

Modification on silicon (100) surfaces was demonstrated by using an atomic force microscope operating in air. Field-enhanced oxidation on silicon surfaces with protection oxide was done locally by biasing a p-type heavily doped silicon tip between −3 and −10 V. Oxide lines of width as small as ∼10 nm were achieved. After a dip in aqueous HF solution, the oxide was etched away; the modification depth, ∼1 nm, was characterized by the same atomic force microscope. Other field induced reactions for patterning are possible.

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Nanometer structures were written on Si(100) surfaces by use of a non-contact-mode atomic force microscope. The silicon oxide was formed beneath the tip by applying a negative bias voltage between a p+ silicon tip and the samples. The writing resolution was mainly determined by the local chemical reactions induced by the tip and a minimum line width of about 10 nm was obtained, which is close to that achieved by scanning tunneling microscope and contact-mode atomic force microscope writing.