Browsing by Author "Kichambare, PD"

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Comparative studies on field emission properties of carbon-based materials
(2000-04-01)
Chen, KH
;
Wu, JJ
;
Chen, LC
;
Wen, CY
;
Kichambare, PD
Comparative studies on field emission properties of various carbon-related materials including diamond, amorphous carbon, SiCN films, SiCN nanorods, and carbon nanotubes are presented. While diamond is well known for its potential use in cold cathodes, the emission current of a hydrogen-treated diamond film is relatively small compared to that of amorphous carbon or diamond-like-carbon film. Meanwhile, carbon nanotubes have demonstrated large emission currents at much lower threshold voltages, showing their potential for applications. However, the emission from carbon nanotubes is subjected to significant decay under long-term operation. The emission current and long-term stability can be improved using a new SiCN compound with nanorod morphology. The effective barrier height and the held enhancement factor derived from the Fowler-Nordheim equation are discussed in this paper. (C) 2000 Elsevier Science S.A. All rights reserved.
Crystalline SiCN: a hard material rivals to cubic BN
(1999-11-01)
Chen, LC
;
Chen, KH
;
Wei, SL
;
Kichambare, PD
;
Wu, JJ
Growth and mechanical properties of SiCN materials prepared by microwave plasma enhanced chemical vapor deposition (CVD) as well as electron cyclotron resonance plasma CVD are reported. Large (several tens of microns), well-faceted ternary SiCN crystals were grown by microwave plasma-enhanced chemical vapor deposition. whereas amorphous SiCN films were deposited by ECR-CVD. The ternary crystalline compound (C; Si)(x)N-y exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the crystalline compound is about 50 at.%, the extent of Si substitution varies and can be as low as 10 at.%. The amorphous SIGN films contain only about 30 at.% N. Nano-indentation studies were employed to investigate the mechanical properties of the SiCN materials. From the load versus displacement curves. we estimated the hardness and the effective modulus of the SIGN crystals to be around 30 and 321.7 GPa, respectively. The corresponding values for the amorphous SiCN were around 22 and 164.4 GPa, respectively. These values are well above most reported values for CN films. (C) 1999 Elsevier Science S.A. All rights reserved.
Enhancement in field emission of silicon microtips by bias-assisted carburization
(2000-11-01)
Kichambare, PD
;
Tarntair, FG
;
Chen, LC
;
Chen, KH
;
Cheng, HC
Ultrathin carbon layers with thicknesses below 50 Angstrom have been deposited on silicon microtip arrays by bias-assisted carburization (BAC) using microwave plasma chemical vapor deposition. The tip radius of these silicon tips is reduced below 55 nm under low deposition temperature. The field emission characterization has been performed in a high-vacuum environment. An enhancement in the field emission is observed of about 3 orders of magnitude in BAC silicon microtips over untreated silicon microtips. With an applied voltage of 1100 V, emission currents of 80 and 120 muA have been achieved for the films grown (at de bias of -200 V for 40 min) with 15% and 25% CH4/H-2 gas ratio, respectively. An emission current of 40 muA has been achieved for the film grown (at de bias of -300 V for 30 min) with 3.5% CH4/H-2 ratio. The BAC silicon emitter has good emission stability at a constant voltage of 1100 V. These investigations indicate that further improvement of this technology will lead to simple and inexpensive field emission display devices. (C) 2000 American Vacuum Society. [S0734-211X(00)10706-1].
Field electron emission from C-based emitters and devices
(2001)
Chen, LC
;
Hong, WK
;
Tarntair, FG
;
Chen, KJ
;
Lin, JB
We present the fabrication, characterization and field emission properties of various C-based emitters and devices, which include (1) the diode-type emitters consisting of arrays of carbon-coated Si microtips and carbon nanotubes (CNTs), (2) CNT triodes. and (3) thin-film-transistor (TFT)-controlled CNT field emission devices (FEDs). All the CNTs were deposited by microwave plasma-enhanced chemical vapor deposition. For the first type, each array contains 50 x 50 emitting cells and each individual cell is 3 microns square. Compared to the Si microtips with bias-assisted carburization or diamond cladding, enhancement in field emission by several orders of magnitude of the CNTs arrays was observed. While the diode-type CNT emitters easily achieve the goal of drawing high electron emission current at low macroscopic field, their long-term stability is not satisfactory for practical applications. For the triode-type CNT-FEDs, vertically aligned CNTs with controlled length were directly grown on the Fe-coated Si substrate pre-patterned by photolithography and etching using oxide as the gate insulator, and the emission current from the CNTs was controlled via the gate voltage. For the TFT-controlled CNT-FEDs, CNTs were selectively grown on the drain region of the TFT and the emission current from the CNTs was controlled via the TFT drain current. It should be mentioned that the fabrication procedures are straightforward and can be integrated with current technologies in the well-established semiconductor industry. Both the triode-type CNTs as well as the TFT-controlled CNT-FEDs have demonstrated improved controllability and stability while maintaining high emission current density.