Electron Field Emission Characterization of Nanocrystalline Diamond Thin Film Cold Cathode Devices
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Characterization has been carried out primarily with Raman spectroscopy. Fig. I shows the Raman spectra oftwo different DTC films and a polycrystalline diamond film. The nitrogen/oxygen flow ratios shown are N2 = 10 and 33 as indicated on the caption. Raman spectra show three broad peaks at 1190, 1330 and 1550 cm-'. The 1550 cm-' peak has a FWHM of 030 cm-'. This peak also appeared for DTC grown from a CH 4/N2 mixture[16]. The lack of a distinct1332 cm-' peak indicates a disturbance of the cubic symmetry of the The 1190 peak is believed to be an amorphous phase. The 1550 cm-' peak is usually attributed to a sp2 bonded material. In addition to Raman spectroscopy X- ray diffraction (XRD) was performed. XRD was
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O06 .4;:0.
N!
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Polycrystalline Dian
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recorded by the Debye-Scherrer method for Cu
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RAMAN SHIFT (cm"')
Ka radiation. Two components of diffraction appeared on the pattern: scattering around the central beam and a set of weak broad peaks corresponding to the cubic diamond lines 111, 220, 331 and 331. The 220 line was shifted toward larger 0. No graphitic phase scattering was observed. Currently films grown by hot filament CVD (HFCVD) are being evaluated. The films are grown on polished Mo substrates. The growth conditions are P=20 Torr at 2% methane concentration. The substrate temperature is 700' C. The Raman spectra is shown in Fig 2.
Figure 1. Comparison of Raman Spectra for Two DTC films and a polycrystall ine diamond film used in this Study. The NA()2 ratios are indicated.
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ELECTRON FIELD EMISSION RESULTS Electron field emission characterization has been carried out using diode and triode configurations in a high vacuum system (P=2 x 10.7 Torr). The I-V curve for a DTC ( N 2/02 = 10) film is shown in Fig.3. Further details of field emission characterization in the diode configuration are reported elsewhere. The I-V curves for the HFCVD film are shown in Fig 4. Several methods to fabricate a simple
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Figure 2. Ramar I Spectra film grown by
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triode device, without the use of lithographic techniques, were attempted. The first method involved depositing thin (
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