No abstract

As previously demonstrated, non-diamond carbon (NDC) films deposited at low temperatures 200-300 °C on silicon tips reduced the threshold of field emission. In this paper we will present the results of the study of field emission from flat NDC films prepared by VHF CVD. Emission measurements were performed in a diode configuration at approximately 10−10 Torr. NDC films were deposited on ceramic and on c-Si substrates sputter coated with layers of Ti, Cu, Ni and Pt. The back contact material influences the emission characteristics but not as a direct correlation to work function. A model of field emission from metal-NDC film structures will be discussed.

No abstract

No abstract

The effect of material and surface morphology of the back contact on field emission has been studied in carbon films deposited by very high frequency chemical vapor deposition at low temperature. The emission current was measured as a function of applied field for carbon films deposited simultaneously on various substrates coated with metals having different work functions ͑Ti, Cu, Ni, and Pt͒. Different metals demonstrated different types of microstructure and surface morphology. Therefore, the effect of back contact morphology was especially studied. The material of the back contact influenced the emission properties, but no direct correlation between emission and the work function of metal was observed. The field emission threshold was found to be affected by the roughness of the back contact: a Ti contact with 270 nm roughness showed emission threshold of E th ϭ3 V/m, while a contact made of the same material, but with roughness of ϳ2.5 nm had E th ϭ13 V/m.

No abstract

Carbon films deposited at relatively low temperatures were studied as a coating for polysilicon substrates to provide enhancement of the electron field emission. Undoped and phosphor doped polysilicon substrates were coated by carbon films grown by a very high frequency chemical vapor deposition process. Critical process parameters include substrate temperature of 225°C, pressure of 56 mTorr, loaded power of 2 W/cm 2 , and discharge frequency of 56 MHz. The substrates were pretreated prior to film deposition, and bias enhanced nucleation was performed in hydrogen/C 6 H 14 plasma. A carbon layer was grown to a thickness of 700 nm. Field emission measurements were performed in an ultrahigh vacuum chamber equipped with an electron gun, a carousel for five samples, and a Faraday cup. A multigrid quasispheric energy analyzer was used for Auger electron spectroscopy and electron energy loss spectroscopy characterization. Additionally, before and after field emission measurements, the secondary emission coefficient was measured by a scanning electron beam, which provided a two-dimensional map of the sample surface. The field emission current was measured in a diode configuration using a spacer thickness of 45-55 m through a current collection window 2ϫ5 mm 2 . Emission current-voltage curves were measured from three different regions of every sample by shifting the current collection window over the sample. A surface conditioning effect was observed, resulting in stabilization and better reproducibility of the emission current-voltage characteristics. The most significant changes in emission characteristics were observed in undoped polysilicon substrates with carbon coatings. Low deposition temperatures make this coating process very attractive because of its compatibility with addressing circuitry based on either silicon or poly-, microcrystalline, or amorphous silicon.

No abstract