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Liu J.L.,University of Science and Technology Beijing | Li C.M.,University of Science and Technology Beijing | Chen L.X.,University of Science and Technology Beijing | Wei J.J.,University of Science and Technology Beijing | And 5 more authors.
Diamond and Related Materials | Year: 2013

Abstract High-quality polycrystalline diamond film has been extremely attractive to many researchers, since the maximum transition frequency (f T) and the maximum frequency of oscillation (fmax) of polycrystalline diamond electronic devices are comparable to those of single crystalline diamond devices. Besides large deposition area, DC arc jet CVD diamond films with high deposition rate and high quality are one choice for electronic device industrialization. Four inch free-standing diamond films were obtained by DC arc jet CVD using gas recycling mode with deposition rate of 14 μm/h. After treatment in hydrogen plasma under the same conditions for both the nucleation and growth sides, the conductivity difference between them was analyzed and clarified by characterizing the grain size, surface profile, crystalline quality and impurity content. The roughness of growth surface with the grain size about 400 nm increased from 0.869 nm to 8.406 nm after hydrogen plasma etching. As for the nucleation surface, the grain size was about 100 nm and the roughness increased from 0.31 nm to 3.739 nm. The XPS results showed that H-termination had been formed and energy band bent upwards. The nucleation and growth surfaces displayed the same magnitude of square resistance (R s). The mobility and the sheet carrier concentration of the nucleation surface were 0.898 cm/V s and 1013/cm2 order of magnitude, respectively; while for growth surface, they were 20.2 cm/V s and 9.97 × 1011/cm2, respectively. The small grain size and much non-diamond carbon at grain boundary resulted in lower carrier mobility on the nucleation surface. The high concentration of impurity nitrogen may explain the low sheet carrier concentration on the growth surface. The maximum drain current density and the maximum transconductance (gm) for MESFET with gate length LG of 2 μm on H-terminated diamond growth surface was 22.5 mA/mm and 4 mS/mm, respectively. The device performance can be further improved by using diamond films with larger grains and optimizing device fabrication techniques. © 2012 Elsevier B.V. All rights reserved. Source


Li C.M.,University of Science and Technology Beijing | Liu J.L.,University of Science and Technology Beijing | Chen L.X.,University of Science and Technology Beijing | Wei J.J.,University of Science and Technology Beijing | And 4 more authors.
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

With the development of information and communication technology, conventional semiconductors such as Si and GaAs cannot satisfy the requirement of high-frequency and high-power electronic devices. By contrast, diamond film has been considered to be a potential material alternative due to the highest Johnson and Keyse figures of merit. In this paper, H-terminated polycrystalline diamond films with different quality were prepared by DC arc jet CVD through adjusting the deposition conditions. The conductive behaviour of p-type channel on H-terminated diamond surface was compared and analyzed based on the N-related impurity and spontaneous polarization model. After that, MESFETs (metal-semi-conductor field effect transistor) were fabricated on H-terminated diamond and the radio frequency (RF) performance was evaluated. The cut off frequency (fT) of 11 GHz and the maximum oscillation frequency (fmax) of 18.5 GHz for MESFET in our situation were obtained. It was found that equivalent circuit elements were lower or comparable with the reported values for the FETs with the highest fT and fmax except the gate capacitance, which indicates that the carrier mobility should be improved further for high-frequency devices application. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Zhu R.H.,University of Science and Technology Beijing | Li C.M.,University of Science and Technology Beijing | Chen L.X.,University of Science and Technology Beijing | Liu J.L.,University of Science and Technology Beijing | And 3 more authors.
Applied Surface Science | Year: 2015

Solid particle erosion behaviors of the nucleation and growth surface of free-standing diamond films as a function of erosion time were studied by a laboratory designed blast type erosion apparatus. The surface roughness and the transmission loss were used to evaluate the extent of erosion performance. Results showed that the erosion damage features generated by impact appeared after erosion for 5 s and 30 s for nucleation and growth surface of diamond films respectively, and primarily occurred at grain boundaries in the form of micro-cracks. Then the local chipping of small sections on the border of cracks was followed resulting in material removal. The threshold erosion time, to maintain the transmission at 10.6 μm still above 60%, was 60 s and 300 s for nucleation and growth surface of diamond films. The growth surface of diamond films exhibited about 5 times higher erosion resistance for ending up with relatively lower surface roughness and transmission loss compared with the nucleation surface, which was in accordance with the ratio of grain sizes. © 2015 Elsevier B.V. All rights reserved. Source


Liu J.L.,University of Science and Technology Beijing | Li C.M.,University of Science and Technology Beijing | Zhu R.H.,University of Science and Technology Beijing | Guo J.C.,University of Science and Technology Beijing | And 7 more authors.
Applied Surface Science | Year: 2013

Diamond has been considered to be a potential material for high-frequency and high-power electronic devices due to the excellent electrical properties. In this paper, we reported the radio frequency (RF) characteristic of metal-semiconductor field effect transistor (MESFET) on polycrystalline diamond films prepared by direct current (DC) arc jet chemical vapor deposition (CVD). First, 4 in polycrystalline diamond films were deposited by DC arc jet CVD in gas recycling mode with the deposition rate of 14 μm/h. Then the polished diamond films were treated by microwave hydrogen plasma and the 0.2 μm-gate-length MESFET was fabricated by using Au mask photolithography and electron beam (EB) lithography. The surface conductivity of the H-terminated diamond film and DC and RF performances of the MESFET were characterized. The results demonstrate that, the carrier mobility of 24.6 cm2/V s and the carrier density of 1.096 × 1013 cm-2 are obtained on the surface of H-terminated diamond film. The FET shows the maximum transition frequency (fT) of 5 GHz and the maximum oscillation frequency (fmax) of 6 GHz at VGS = -0.5 V and V DS = -8 V, which indicates that H-terminated DC arc jet CVD polycrystalline diamond is suitable for the development of high frequency devices. © 2013 Elsevier B.V. All rights reserved. Source


Liu J.L.,University of Science and Technology Beijing | Li C.M.,University of Science and Technology Beijing | Guo J.C.,University of Science and Technology Beijing | Zhu R.H.,University of Science and Technology Beijing | And 7 more authors.
Applied Surface Science | Year: 2013

The surface conductivity of polished polycrystalline diamond films after atomic hydrogen bombardment for different time was compared and the carrier transport characteristic beneath the H-terminated diamond film surface was investigated correspondingly. It is found that, as the bombardment time increases, the surface roughness of diamond films first decreases due to disappearance of scratches, and then increases because of appearance of protrusions produced by plasma preferentially etching. Mean while the total C-H bonding concentration on the diamond surface increases gradually until it is saturated when the bombardment time is up to 30 min. The almost invariable carrier density is obtained for all samples treated for different time, which indicates the monohydride (CH) mode responsible for surface conductivity forms when hydrogen treatment starts. While for the carrier mobility, it shows the inverse trend with change of the surface roughness. A model based on the surface roughness scattering was proposed to explain the relationship between the surface conductivity and roughness. Combining with the carrier mobility and density, the lowest square resistance of 13.85 κΩ is obtained for polycrystalline diamond film when it is treated for 30 min. It is speculated that the surface conductivity can be further enhanced by reducing the surface roughness. © 2013 Elsevier B.V. All rights reserved. Source

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