Effect of high substrate bias and hydrogen and nitrogen incorporation on filtered cathodic vacuum arc deposited tetrahedral amorphous carbon films

Effect of high substrate bias and hydrogen and nitrogen incorporation on density of states and field-emission threshold in tetrahedral amorphous carbon films

“…The decrease in the value of N ͑E F ͒ with the increase in hydrogen incorporation is accompanied with the increase in sp 3 content evaluated from XAES studies. 26 This is found to be consistent with the report by Silva and Amaratunga 32 who reported reduction in the bulk density of states in ta-C:H or a-C:H film due to a reduction in sp 2 fraction. Figure 5͑a͒ shows the variation of the field-emission current density ͑J͒ versus electric field ͑E͒ characteristics of Table II along with the value of N ͑E F ͒ and sp 3 content evaluated.…”

“…Figure 5͑a͒ shows the variation of the field-emission current density ͑J͒ versus electric field ͑E͒ characteristics of Table II along with the value of N ͑E F ͒ and sp 3 content evaluated. 26 It is evident from Table II that hydrogen incorporation in asgrown ta-C films continuously reduces the values of E turn-on , slope m of FN plots, and increases the values of J and ␤ with the increase in hydrogen partial pressure used in depositing ta-C:H films. The value of evaluated for an ideal plane emitter with a field-enhancement factor of one in ta-C:H film remains the same at 0.10 eV and does not change with hydrogen incorporation.…”

“…The details about the FCVA system and the other deposition conditions have been described earlier. [25][26][27][28] During the deposition of ta-C:H and ta-C:N films, the substrate bias was kept constant at Ϫ300 V and the arc current ͑ϳ75 A͒ and magnetic field ͑ϳ350 G͒ in the S-bend duct were also kept constant. The thickness of the films is found to be in the range of 500Ϯ 100 Å as measured by a Talystep ͑Rank Taylor and Hobson͒ thickness profiler.…”

“…Thus, the values of N ͑E F ͒ of as-grown ta-C film evaluated in the present study are consistent with the values of N ͑E F ͒ of as-grown ta-C films deposited using the L-bend FCVA process reported by Veerasamy et al 33 The minimum values of N ͑E F ͒ are observed in as-grown ta-C films deposited at Ϫ200 V substrate bias, where the sp 3 content evaluated from XAES studies is found to be the maximum. 26 Fallon et al 1 showed, using a FCVA system, that the optimal ion energy for the highest sp 3 -bonded fraction is close to ϳ100 eV. This converts to an applied substrate bias of about 80 V based on the calculation that the as-generated carbon ion, in the case of a normal continuous cathodic arc, is 20-25 eV.…”

“…The properties investigated are also system dependent. 2 One of the first systematic reports of ta-C films at high substrate bias ͑Ϫ300 V͒ of reflectance and photoluminescence, 25 x-ray photoelectron spectroscopy ͑XPS͒, x-ray Auger induced electron spectroscopy ͑XAES͒, and Raman spectroscopy studies, 26 plasma diagnostic studies 27 and electrical and mechanical properties 28 have been published recently. The current work complements it, especially with reference to the possibility of use of this material as electronic material by studying the defect density measured using space-charge-limited-conduction ͑SCLC͒ studies and the field assisted electron emission of as-grown ta-C, ta-C:H, and ta-C:N films.…”