Shaul Michaelson

Hydrogen bonding at grain surfaces and boundaries of nanodiamond films detected by high resolution electron energy loss spectroscopy

Hydrogenated nanodiamond films consisting of 300 and 10–30nm grain sizes were examined by high resolution electron energy loss spectroscopy. C–H stretching modes were identified at 350, 360, and 375meV. The mode at 375meV was enhanced in the case of 10–30nm grain size and it is stable up to in situ annealing to >800°C. Complete hydrogen desorption occurs upon annealing to 1000°C. Exposure of the nanodiamond film to atomic hydrogen results in a strong quenching of the 375meV C–H mode, most likely due to preferential etching of (sp2)-carbon-hydrogen at the surface and grain boundaries of the films.

Nitrogen termination of single crystal (100) diamond surface by radio frequency N2 plasma process: An in-situ x-ray photoemission spectroscopy and secondary electron emission studies

In this letter, we report the electronic and chemical properties of nitrogen terminated (N-terminated) single crystal (100) diamond surface, which is a promising candidate for shallow NV− centers. N-termination is realized by an indirect RF nitrogen plasma process without inducing a large density of surface defects. Thermal stability and electronic property of N-terminated diamond surface are systematically investigated under well-controlled conditions by in-situ x-ray photoelectron spectroscopy and secondary electron emission. An increase in the low energy cut-off of the secondary electron energy distribution curve (EDC), with respect to a bare diamond surface, indicates a positive electron affinity of the N-terminated diamond. Exposure to atomic hydrogen results in reorganization of N-terminated diamond to H-terminated diamond, which exhibited a negative electron affinity surface. The change in intensity and spectral features of the secondary electron EDC of the N-terminated diamond is discussed.

Near coalescent submicron polycrystalline diamond films deposited on silicon: Hydrogen bonding and thermal enhanced carbide formation

The influence of high temperature annealing up to 1200 °C in vacuum on ∼100 nm nearly continuous thick diamond films consisting of 30–50 nm crystallites, deposited onto silicon substrates is reported. The hydrogen bonding and phase composition of the films were studied with Raman spectroscopy, while the surface microstructure and composition were studied with high resolution scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS), respectively. Annealing to 800–900 °C of ∼100 nm thick films results in a decrease in the intensities of the peaks associated with hydrogen bonding (Raman), as well as changes to the morphological microstructure at the film surface. Heating the films to 1000 °C resulted in the complete disappearance of the Raman peaks associated with hydrogen bonding at grain boundaries, and an increase in the relative intensity of the diamond peak relative to the graphite-related D and G Raman peaks, concomitant with changes to the ...

Fabrication of a nanometer thick nitrogen delta doped layer at the sub-surface region of (100) diamond

In this letter, we report on the proof of a concept of an innovative delta doping technique to fabricate an ensemble of nitrogen vacancy centers at shallow depths in (100) diamond. A nitrogen delta doped layer with a concentration of ∼1.8 × 1020 cm−3 and a thickness of a few nanometers was produced using this method. Nitrogen delta doping was realized by producing a stable nitrogen terminated (N-terminated) diamond surface using the RF nitridation process and subsequently depositing a thin layer of diamond on the N-terminated diamond surface. The concentration of nitrogen on the N-terminated diamond surface and its stability upon exposure to chemical vapor deposition conditions are determined by x-ray photoelectron spectroscopy analysis. The SIMS profile exhibits a positive concentration gradient of 1.9 nm/decade and a negative gradient of 4.2 nm/decade. The proposed method offers a finer control on the thickness of the delta doped layer than the currently used ion implantation and delta doping techniques.

HR-EELS investigations of hydrogenated nanodiamond films

In this paper we review our recent high resolution electron energy loss spectroscopy (HR-EELS) studies of hydrogenated diamond film surfaces with grain size ranging from micro- to nanometer size. We present our vibrational peaks assignments through isotopic exchange studies of surface species. Special attention was paid to establish the sensitivity of the vibrational losses to defects in diamond structure. The bonding configurations of C and H species located at grain boundaries were investigated by analyzing the stretching modes of C–H (or C–D) vibrations of diamond films consisting of grains from the micro- to nanometric size. Then, we discuss nanosize effect detected by HR-EEL spectroscopy for films composed of different nanodiamond grain size. Thermal stability and diamond phase recovery upon hydrogen adsorption/desorption phenomena was studied for nano- and sub-micrometer crystalline diamond films. Eventually, HR-EELS analysis was applied to study the nanometric nascent stage of hetero-epitaxial diamond film deposition on 3C-SiC(100) substrates.

Fabrication of microchannels in polycrystalline diamond using pre-fabricated Si substrates

In this paper, we report on a simple, feasible method to fabricate microchannels in diamond. Polycrystalline diamond microchannels were produced by fabricating trenches in a Si wafer and subsequently depositing a thin layer of diamond onto this substrate using the hot filament vapor deposition technique. Fabrication of trenches in the Si substrate at different depths was carried out by standard photolithography, and the subsequent deposition of the diamond layer was performed by the hot filament chemical vapor deposition technique. The growth mechanism of diamond that leads to the formation of closed diamond microchannels is discussed in detail based on the Knudsen number and growth chemistry of diamond. Variations in the crystallite size, crystalline quality, and thickness of the diamond layer along the trench depths were systematically analyzed using cross-sectional scanning electron microscopy and Raman spectroscopy. Defect density and formation of non-diamond forms of carbon in the diamond layer were ...

Bonding and Concentration of Hydrogen and Thermal Stability of Nanocrystalline Diamond Films

One of the central themes in synthetic diamond-related basic research is the interaction of hydrogen with diamond. This is crucial since the chemical vapor deposition (CVD) diamond is often grown in a hydrogen-containing environment so it is present within the material. Also hydrogen has a major role in controlling the interfacial, electronic, and optical properties of the as-deposited films on which many of the applications depend. Hydrogen is a main player in the “magic” of diamond formation by CVD and its role has been investigated both experimentally and theoretically.

Nanodiamond Films Deposited from Energetic Species: Material Characterization and Mechanism of Formation

Publisher Summary Nanocrystalline carbon film of a prevailing diamond character can be deposited by direct-current glow-discharge (DC-GD) chemical vapor deposition (CVD) from a methane–hydrogen mixture. This chapter discusses the phase evolution of the films, microstructure, hydrogen content, and bonding in the films. The characterization of the nanodiamond films is very complex and requires the use of a number of microstructural analytical methods. A full picture of film properties can only be attained from a combination of characterization methods. The advantages and complementarities of the characterization tools used are also discussed in the chapter. The nanodiamond films deposited from energetic species (DC-GD method) display 80% diamond character, and no surface pretreatment is necessary for inducing their formation. The surface of the films is amorphous in nature. From a microscopic perspective, nanodiamond film growth from energetic species is explained as a subsurface process in terms of a four-step cyclic process.