Materials Chemistry and Physics 72 (2001) 214–217 Successive current–voltage measurements of a thick isolated diamond film Bohr-Ran Huang a,∗ , Wen-Cheng Ke b , Jung-Fu Hsu a , Wei-Kuo Chen b a Institute of Electronics and Information Engineering, National Yunlin University of Science and Technology, 123 University Road, Section 3, Touliu, Yunlin 640, Taiwan b Department of Electrophysics, National Chiao Tung University, Hsinchu 300, Taiwan Abstract Polycrystalline diamond films were deposited on p-type (1 0 0) silicon substrate using a methane/hydrogen gas mixture in a microwave plasma-assisted chemical vapor deposition system. After the back-etched process, the Al contacts were evaporated on both sides of a 150 m thick isolated diamond film for consecutive high-voltage measurements. It was found that the current–voltage (I–V) characteristics of the Al/diamond/Al structure exhibited two Schottky barrier diodes in a back-to-back configuration. Since the top diamond surface possessed better diamond quality than the bottom surface, the top Schottky diode with a breakdown voltage of 897 V and a lower breakdown voltage of -515 V for the bottom Schottky diode was observed for the first I–V measurement. However, the breakdown voltage was decreased by 37 and 140 V for the top and bottom Schottky diodes after the consecutive sixth repeated measurements. It was found that the oxygenated phenomenon was more prominent; in addition, the quality of the isolated diamond film was also degraded after the consecutive high-voltage measurements. It was indicated that decrease of the breakdown voltage was due to the oxidation layer and the non-diamond components on both surfaces of the isolated diamond film. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Plasma-assisted CVD; AFM; XPS 1. Introduction Diamond with a wide energy gap (5.5 eV) has a unique combination of properties, such as high breakdown voltage, high thermal conductivity, and excellent radiation hardness etc. [1,2]. In the recent years, Si and GaAs was generally used as the semiconducting material, however, these mate- rials have restricted applications in high voltage, high tem- perature, high radiation, and/or corrosive environments. To overcome these limitations, wide energy bandgap materials are preferred. Among them, diamond has the highest break- down voltage, the highest thermal conductivity and radiation hardness which has potential as a semiconducting material. It was known that the electrical breakdown is one of the main limitations of high-voltage device operation such as in high-power and high-voltage electronic devices. Several researches have been studied for the high-voltage charac- teristics of the diamond films [3–5]. It was known that the breakdown voltage was dependent on the surface morphol- ogy, film quality, and thickness [6]. However, successive current–voltage measurements were important for the stabil- ity of the electronic device. In this research, the successive ∗ Corresponding author. Tel.: +886-5534-2601; fax: +886-5531-2063. E-mail address: huangbr@pine.yuntech.edu.tw (B.-R. Huang). current–voltage measurements and the correlation to the physical characteristics of the isolated diamond film will be carefully studied. 2. Experimental details Undoped diamond films were deposited on a 2 in. (1 0 0) p-type silicon wafer using a microwave plasma chemical vapor deposition system. Prior to deposition, the silicon substrate was pretreated by the photoresist in which 0.1 m diamond powder is suspended in order to enhance the nu- cleation density. Typical deposition conditions were shown as follows: gas flow rates: CH 4 /H 2 : 20/600 sccm; pres- sure: 120 Torr; deposition temperature: 900 ◦ C, deposition time: 200 h. The isolated diamond film was then obtained by etching the silicon substrate with the KOH solution (44% by weight to water) at 60 ◦ C. The Al contacts with 0.5 mm diameter were obtained on both sides of the iso- lated diamond film by vacuum thermal evaporation through a shadow mask. Following, the electrical properties of the Al/isolated diamond/Al structure were measured on a mi- croprobe station with Source-Measure Unit Keithley 236 and 237 system in the voltage range of ±1100V. The step delay time between each electrical measurement is 30 s. 0254-0584/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0254-0584(01)00439-4