Enhancement of electron emission from near-coalescent nanometer thick continuous diamond films

Chemical Vapor Deposition

et al. 2008

In the present work we review our recent studies of the incorporation of hydrogen and its bonding configuration in diamond films composed of diamond grains of varying size. Polycrystalline-diamond films are deposited by three different methods; hot filament (HF), microwave (MW) and direct current glow discharge (DCGD)CVD. The size of the diamond grains which constitute the films varies in the following way; hundreds of nanometers in the case of HFCVD (''submicrometer size'', $300 nm), tens of nanometers in the case of MWCVD (3-30 nm), and a few nanometers in the case of DCGDCVD (''ultra nanocrystalline diamond'', $5 nm). Raman spectroscopy (RS), secondary ion mass spectroscopy (SIMS), and high-resolution electron energy loss spectroscopy (HREELS) are applied to investigate the hydrogen trapping in the films. The hydrogen retention of the diamond films increases with decreasing grain size, indicating the likelihood that hydrogen is bonded and trapped in grain boundaries, as well as on the internal grain surfaces. RS and HREELS analyses show that at least part of this hydrogen is bonded to sp 2 -and sp 3 -hybridized carbon, thus giving rise to typical C-H vibration modes. Both vibrational spectroscopies show the increase of sp 2 C-H modes in transition from sub-micrometer to ultra nanocrystalline grain size. The impact of diamond grain size on the shape of the RS and HREELS hydrogenated diamond spectra is discussed. In addition, the dependence of electron emission properties on film thickness and diamond grain size is reported.

“…Figure 12 summarizes the results of electron emission induced by four different methods. [16] The absolute QPY value at a photon energy of 8.85 eV increases with film Full Paper Fig. 9.…”

Section: Enhancement Of Electron Emission Frommentioning

confidence: 97%

Section: Enhancement Of Electron Emission Frommentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Impact of Diamond Grain Size on Hydrogen Concentration, Bonding Configuration, and Electron Emission Properties of Polycrystalline‐Diamond Films

Michaelson

Ternyak

Chemical Vapor Deposition

et al. 2008

Section: Introductionmentioning

confidence: 99%

Hydrogen concentration and bonding configuration in polycrystalline diamond films: From micro-to nanometric grain size

Michaelson

Ternyak

Journal of Applied Physics

et al. 2007

Self Cite

The present work studies the incorporation of hydrogen and its bonding configuration in diamond films composed of diamond grains of varying size which were deposited by three different methods: hot filament ͑HF͒, microwave ͑MW͒, and direct current glow discharge ͑dc GD͒ chemical vapor deposition ͑CVD͒. The size of diamond grains which constitute the films varies in the following way: hundreds of nanometers in the case of HF CVD ͑"submicron size," ϳ300 nm͒, tens of nanometers in the case of MW CVD ͑3-30 nm͒, and a few nanometers in the case of dc GD CVD ͑"ultrananocrystalline diamond," ϳ5 nm͒. Raman spectroscopy, secondary ion mass spectroscopy, and high resolution electron energy loss spectroscopy ͑HR-EELS͒ were applied to investigate the hydrogen trapping in the films. The hydrogen retention of the diamond films increases with decreasing grain size, indicating that most likely, hydrogen is bonded and trapped in grain boundaries as well as on the internal grain surfaces. Raman and HR-EELS analyses show that at least part of this hydrogen is bonded to sp 2 -and sp 3 -hybridized carbon, thus giving rise to typical C u H vibration modes. Both vibrational spectroscopies show the increase of ͑sp 2 ͒-C u H mode intensity in transition from submicron to ultrananocrystalline grain size. The impact of diamond grain size on the shape of the Raman and HR-EELS hydrogenated diamond spectra is reported and discussed.

The influence of surface conditioning on the thermionic electron emission from polycrystalline diamond films

Bar-Hama

Physica Status Solidi (a)

Hoffman

2012

Self Cite

Thermionic electron emission (TEE) properties of as deposited, bare surface, in situ hydrogen‐terminated and in situ oxygen‐terminated polycrystalline diamond (Poly‐Di) films surfaces are reported. Continuous Poly‐Di films of a thickness of ∼200 nm grown on B‐doped Si substrates by hot‐filament chemical vapor deposition (HF CVD) were used. The TEE measurements were carried out in the 500–650 °C temperature range by recording the energy spectra of the electrons emitted using a hemispherical energy analyzer under ultra‐high vacuum (UHV) conditions. As‐deposited Poly‐Di surfaces may exhibit variations in their TEE properties depending on history and surface conditioning, thus indicating the need to control the diamond surface chemistry to obtain reproduceable TEE properties. Annealing to 1000 °C results in significant decrease of the TEE intensities, related to thermal desorption of hydrogen and creation of a bare surface. in situ annealing to 1000 °C followed by in situ hydrogenation of the Poly‐Di film surface results in significant enhancement of the TEE. Several cycles of the last procedure show that the TEE of hydrogen‐terminated Poly‐Di surface can be restored, whereas minor decrease in TEE intensity can be associated with slow surface degradation of the Poly‐Di surface following this conditioning. It is suggested that the TEE from hydrogen‐terminated Poly‐Di film may involve two mechanisms. Oxygenation of the bare Poly‐Di film results in low TEE intensities, very similar to those obtained from the bare Poly‐Di film surface, indicating that the TEE process from Poly‐Di film is somehow insensitive to the difference in the surface potential induced by oxygenation and bare surface conditionings.