Galvanic Deposition of Gold on GaAs: A Tip-Induced Lithography Approach

Abstract

A lithography technique based on reduction of metal ions on localized regions of GaAs surfaces is demonstrated. In this technique, an atomic force microscopy (AFM) tip was used to create localized defect patterns on a GaAs surface while operated in air. Subsequent exposure of the semiconductor surface to an Au(III) solution results in the deposition of gold by galvanic displacement reaction on pre-patterned defect areas. [16][17][18][19][20] have been demonstrated as useful approaches in the fabrication of metal structures on various surfaces.The metallization of semiconductor surfaces via the galvanic displacement reaction has been intensively investigated.2,21-23 Galvanic displacement deposition is a relatively simple redox reaction in which noble metal ions in solutions are reduced by the substrate resulting in growth of metal deposits with various surface morphologies. The surface morphology of electroless deposited metals depends on the substrate, composition of the electrolyte, including pH and conditions of deposition eg. temperature, stirring etc.. 24,25 Metallization of semiconductors via galvanic displacement leads to the deposition of metal over the entire surface. Therefore, masking of the surface of semiconductors with specific polymers is required in order to fabricate desired metallic patterns. Use of polymer masks to restrict reduction of gold on a specific area has been applied in most of static/dynamic plow-based lithography techniques. [16][17][18][19] In this work a simple three step process for a deposition of 50 nm wide and 10 nm high gold nanowires on GaAs semiconductor is described. This technique may allow the direct deposition of noble metals such as Au, Ag, or similar on GaAs semiconductor surface. ExperimentalCommercially available n-type GaAs (100) semiconductor wafers (Wafer world Inc, Florida) cut into 1 cm 2 pieces were used as substrates in the present experiments. In order to confirm the deposition of gold onto GaAs via the galvanic displacement reaction, the substrates were cleaned with ethanol and then simply immersed into 5 mM gold chloride trihydrate (HAuCl 4 · 3H 2 O) solution for one hour. All experiments were performed at room temperature (about 22• C). After one hour of immersion, GaAs wafers were removed from the Au-containing solution, carefully washed with distilled water and then with ethanol. The substrates were stored under ethanol for the future scanning electron microscopy (SEM) and X-ray diffraction (XRD) examinations.For the tip-induced lithography on GaAs semiconductor, the following experiments were performed. The substrates were first cleaned * Electrochemical Society Active Member.* * Electrochemical Society Fellow. z E-mail: sdjokic@telus.net with deionized water and sonicated in 95% ethanol solution for 2 minutes to remove the contaminations. The substrates were then dried by blowing N 2 gas and subjected to the three step lithography process. 0.01% Br 2 dissolved in CH 3 OH (BrMeOH) solution was used to clean the GaAs substrate prior to gold deposition....

Formation, Morphology, and Optical Properties of Electroless Deposited Gold Nanoparticles on 3C-SiC

“…Deposition was performed by immersion in a solution containing HF and KAuCl 4 . As expected , gold particles agglomerate preferentially on the antiphase domain boundaries (APBs) present in a large amount on the surface of the thinner 3C-SiC layer. By increasing the SiC layer thickness, instead, the gold particles were homogeneously distributed all over the surface.…”