Low Threshold Field Emission from Amorphous Carbon Films Grown by Electrochemical Deposition
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0956-J09-10
Low Threshold Field Emission from Amorphous Carbon Films Grown by Electrochemical Deposition Hideo Kiyota1, Mikiteru Higashi2, Tateki Kurosu2, and Masamori Iida3 1 Department of Electrical and Electronic Systems, Kyushu Tokai University, 9-1-1 Toroku, Kumamoto, 862-8652, Japan 2 Department of Electronics, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa, 2591207, Japan 3 Department of Information and Network, Tokai University Junior College, 2-3-23 Takanawa, Minato-ku, Tokyo, 108-8649, Japan
ABSTRACT Electrochemical deposition of amorphous carbon (a-C) film is performed by applying a bias voltage to substrate immersed in methanol. Both scanning electron microscopy and Raman results indicate that smooth and homogeneous a-C films are grown on specific substrate materials such as Si, Ti, and Al. Field emission measurements demonstrate excellent emission properties such as threshold fields lower than 5 V/µm. Field enhancement factors are estimated to be 1300–1500; these are attributed to local field enhancements around sp2 carbon clusters that are embedded in the a-C films. Emission properties of a-C films grown on Si exhibit a current saturation under higher applied fields. These saturation behaviors are explained by an effect of a potential barrier formed at the interface between a-C films and substrates. Since the interface barrier is reduced by formation of the TiC interfacial layer, an approach to utilize carbide formation at the interface is verified as useful to improve the emission properties of a-C films. INTRODUCTION Electron field emission from diamond and related carbon materials has attracted much attention because of their outstanding properties such as negative electron affinity, high thermal conductivity, and radiation hardness. Threshold fields for electron emissions from chemicalvapor deposited (CVD) diamond films have been reported as 5–20 V/µm [1-3]. These are considerably lower than those of other materials such as Si (1000 V/µm or greater). Aside from the diamond, amorphous carbon (a-C) is known as an attractive material for the field emitter applications. Regarding emission properties, threshold fields of a-C films are reported respectively as 10–20 V/µm for undoped films and 4 V/µm for N-doped films [4-6]. Growth of the a-C film has been achieved using conventional vapor deposition techniques such as CVD [4], pulse laser deposition [5], and filtered cathodic arc [6]. We have attempted the electrochemical deposition of a-C films to develop alternative techniques for production of carbon materials. The growth of a-C films was performed by applying a DC bias voltage to the substrate immersed in methanol [7]. Similar attempts to synthesize a-C films using organic liquid have been reported by several authors [8-10]. From both scientific and technological viewpoints, those novel attempts have encouraged innovation of deposition techniques for the carbon materials. In addition, electrochemical deposition offers numerous advantages, including simplicity of the deposition apparatus, lo
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