Preferential Adhesion of Gold Nanoparticles Using Lithographically Patterned Substrates
- PDF / 1,639,823 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 21 Downloads / 259 Views
Preferential Adhesion of Gold Nanoparticles Using Lithographically Patterned Substrates Johan Pihl, Mohammad S. Kabir and S.H. Magnus Persson Dept of Microelectronics and Nanoscience, Chalmers Univ of Technology, Gothenburg, Sweden ABSTRACT A method of aligning small amounts of colloidal particles between narrowly spaced electrodes using a combination of conventional nanofabrication and self-assembled monolayers has been developed. Transport measurements were performed on several devices INTRODUCTION Colloidal nanoparticles is a class of particles that has received an increasing attention over the last years. It is possible to produce nanoparticles in a variety of different materials and sizes by different methods [6-8] and the possible applications can be found in numerous areas such as nanoelectronics [9,10], sensor technology [11] and optics [12] to mention only a few. It is desirable to be able to assemble nanoparticles in an arbitrary way, and examples of this have been demonstrated [13-17], but seldom involving parallel techniques on the few- or singleparticle scale. In this article, we report a parallel and reproducible assembly of gold nanoparticles on the few-particle scale between narrowly spaced electrodes. This is achieved by patterning either poly(methylmethacrylate) (PMMA) or self-assembled monolayers [18] with electron beam lithography, followed by chemical vapor deposition of another self-assembled monolayer, thereby producing narrow lines for which the nanoparticles have a high affinity. EXPERIMENTAL PROCEDURES Silicon [100] wafers with a thermally grown oxide of 100 nm were used as substrates, and the wafers were cleaned prior to use by oxygen plasma stripping. Contact pads were defined using photolithography and metal evaporation of 10 nm of Cr and 50 nm of Au followed by liftoff. Electrodes with 30-60 nm gaps were fabricated by direct writing electron beam lithography using a JEOL JBX-5DII electron beam lithography system followed by subsequent metal evaporation and liftoff. The resist system consisted of a 140 nm bottom layer of methacrylic acid copolymer (MAA) and a top layer of 60 nm of 950K PMMA, and the electrodes consisted of 5 nm of Cr and 10-20 nm of Au. As for the final patterning step, two different methods were used. In the first method, lines were defined across the electrodes in a 90 nm thick layer of 950K PMMA by electron beam lithography and ultrasonically assisted development of PMMA in a 1:3 mixture of methylisobutylketone:isopropanol [1-3]. A monolayer of 3-aminopropyltriethoxysilane or 3-mercaptopropyltriethoxysilane was deposited by room temperature chemical vapor deposition utilizing a dry setup consisting of a rotary pump and a glass container [4]. The samples were then immersed in a solution of gold nanoparticles with mean diameters of 5 or 10 nm in a sodium azide water solution [5] for 1-12 hours. Finally, the PMMA was lifted off by soaking the samples in acetone for about 30 minutes, leaving the lines of gold nanoparticles across the electrodes.
Y6.7.1
In the second me
Data Loading...
