Nanodevice fabrication on hydrogenated diamond surface using atomic force microscope
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Nanodevice fabrication on hydrogenated diamond surface using atomic force microscope Minoru Tachiki, Tohru Fukuda, Hokuto Seo, Kenta Sugata, Tokishige Banno, Hitoshi Umezawa and Hiroshi Kawarada School of Science & Engineering, Waseda University, Tokyo, Japan. CREST, Japan Science and Technology Corporation (JST), Japan E-mail: [email protected] ABSTRACT Nanofabrication on a hydrogen-terminated diamond surface is performed using an atomic force microscope (AFM) anodization. Locally insulated areas less than 30 nm are successfully obtained. Side-gated field effect transistors (FETs) are fabricated using the local anodization, and they operate successfully. Single hole transistors composed of one side-gated FET and two tunneling junctions are also fabricated and operate at liquid nitrogen temperature (77 K). INTRODUCTION Recently, nanofabrication technology using a scanning probe microscope (SPM) has attracted special interest [1-4]. The fabrication of several nanoscale devices has been reported based on this technique, including nanoscale FETs and single electron transistors (SETs), which have been fabricated by the local anodization of Si, Ti and compound semiconductors [5-8]. Hydrogen termination (H-termination) of diamond surfaces is important because it can stabilize the surface structure. Furthermore, H-terminated diamond is also attractive for electrical applications because it induces p-type surface conduction even in undoped diamond [9-11]. Recently, our group has demonstrated the fabrication and the operation of field-effect transistors (FETs) using a surface conductive layer, and has obtained high transconductance [12,13]. The thickness of this surface conductive layer was estimated to be less than 10 nm, and the surface hole density to be 1013 cm-2 [11]. On the other hand, an oxygen-terminated (O-terminated) diamond surface is insulating. This means that diamond has an advantage over other semiconductor materials in the fabrication of a surface nanostructure using a SPM-based processing technology. Since undoped diamond is basically an insulating material, we can conclude that H-terminated diamond has a semiconductor-on-insulator structure. In the case of Si, special techniques such as separation by implanted oxygen (SIMOX) etc. are needed to fabricate the electrically isolated thin conducting layer. In diamond, an electrically isolated surface conductive layer is easily obtained by eliminating the surface H-termination. Recently, local anodization on H-terminated diamond surface was performed using a metal (Au, Rh, etc.) coated conductive atomic force microscope (AFM) cantilever by applying voltage bias to the sample surface [14-17]. Up to the present, local insulation (30-60 nm in line width) has been successfully achieved using AFM. The nm scale separation of H-terminated surface and O-terminated surface will produce new types of nanoscale surface quantum devices such as single charge tunneling devices etc.. In the present study, the fabrication and operation of side-gated diamond metal-insulator-
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