The growth of thin films of chemical vapour deposition (CVD) diamond onto flat samples of pure Zr has been studied using various CVD growth conditions in a hot filament reactor. We find that although growth is straightforward, adhesion of the diamond layer onto the Zr is poor, with the diamond layer often delaminating upon cooling. SIMS depth profiles show this to be due to the presence of a strongly-bonded native oxide on the Zr surface which is not removed in the reducing H2 atmosphere during CVD. This, plus the lack of any substantial carbide interfacial layer to ‘glue’ the diamond onto the surface, together with a poor thermal expansion mismatch between Zr and diamond, and the Zr hcp-to-bcc phase transition at ∼860°C, all lead to poor adhesion. Some of these difficulties can be reduced by depositing at lower temperature (<500°C) at the cost of poorer quality diamond.

A method of diamond heteroepitaxial lateral overgrowth is demonstrated which utilizes a photolithographic metal mask to pattern a thin (001) epitaxial diamond surface. Significant structural improvement was found, with a threading dislocation density reduced by two orders of magnitude at the top surface of a thick overgrown diamond layer. In the initial stage of overgrowth, a reduction of diamond Raman linewidth in the overgrown area was also realized. Thermally-induced stress and internal stress were determined by Raman spectroscopy of adhering and delaminated diamond films. The internal stress is found to decrease as sample thickness increases.

The study of combined single-crystalline and polycrystalline chemical vapor deposited (CVD) diamond wafers is reported. Combined CVD diamond wafers up to 75 mm in diameter were grown, which consist of great number of single-crystalline diamond sections grafted in a polycrystalline diamond matrix. The grown combined CVD wafers were characterized by the Raman spectroscopy. It was shown that in the grafting process, the single- and polycrystalline areas of the combined wafer undergo insignificant stresses, which can be released during the thermal annealing process. Fabricated combined CVD diamond can be used in various applications that employ unique properties of diamond and potentially suitable for industrial use.

Laser-induced vibrational excitation of ethylene molecules was integrated to the CVD diamond deposition process for an in-depth understanding of the energy coupling path in chemical reactions and an alternative method to enhance the diamond deposition. On- and off-resonance excitations of ethylene molecules were achieved via tuning the incident laser wavelengths centered at 10.532 µm. With the same amount of laser power absorbed, the chemical reaction is highly accelerated with on-resonance vibrational excitation whereas energy coupling with off-resonance excitations was less efficient in influencing the combustion process. The diamond deposition rate was enhanced by a factor of 5.7 accompanied with an improvement of diamond quality index with the on-resonance excitation at 10.532 μm. The measured flame temperature demonstrated that the resonant vibrational excitation was an efficient route for coupling energy into the reactant molecules and steering the combustion process.

Chemical Vapor Deposited (CVD) diamond growth on (111)-diamond surfaces has received increased attention lately because of the use of N-V related centers in quantum computing as well as application of these defect centers in sensing nano-Tesla strength magnetic fields. We have carried out a detailed study of homoepitaxial diamond deposition on (111)-single crystal diamond (SCD) surfaces using a 1.2 kW microwave plasma CVD (MPCVD) system employing methane/hydrogen/nitrogen/oxygen gas phase chemistry. We have utilized Type Ib (111)-oriented single crystal diamonds as seed crystals in our study. The homoepitaxially grown diamond films were analyzed by Raman spectroscopy, Photoluminescence Spectroscopy (PL), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The nitrogen concentration in the plasma was carefully varied between 0 and 1500 ppm while a ppm level of silicon impurity is present in the plasma from the quartz bell jar. The concentration of N-V defect centers with PL zero phonon lines (ZPL) at 575nm and 637nm and the Si-defect center with a ZPL at 737nm were experimentally detected from a variation in CVD growth conditions and were quantitatively studied. Altering nitrogen and oxygen concentration in the plasma was observed to directly affect N-V and Si-defect incorporation into the (111)-oriented diamond lattice and these findings are presented.

Diamond-like carbon (DLC) has widespread attention as a new material for its application to thin film solar cells and other semiconducting devices. DLC can be produced at a lower cost than amorphous silicon, which is utilized for solar cells today. However, the electrical properties of DLC are insufficient for this purpose because of many dangling bonds in DLC. To solve this problem, we investigated the effects of the fluorine incorporation on the structural and electrical properties of DLC.

We prepared five kinds of fluorinated DLC (F-DLC) thin film with different amounts of fluorine. Films were deposited by the radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) method. C6H6 and C6HF5 were used as source gases. The total gas flow rate was constant and the gas flow rate ratio R (=C6H6 / (C6H6 + C6HF5)) was changed from 0 to 1 in 0.25 ratio steps. We also prepared nitrogen doped DLC (F-DLC) on p-Si using N2 gas as a doping gas to form nitrogen doped DLC (F-DLC) / p-Si heterojunction diodes.

X-ray photoelectron spectroscopy (XPS) showed that fluorine concentration in the DLC films was controlled. Moreover, the XPS analysis of the C1s spectrum at R=2/4 showed the presence of CF bonding. At R=1, CF2 bonding was observed in addition to CF bonding. The sheet resistivity of the films changed from 3.07×1012 to 4.86×109 Ω. The minimum value was obtained at R=2/4. The current-voltage characteristics indicated that nitrogen doped F-DLC of 2/4 and p-Si heterojunction diode exhibited the best rectification characteristics and its energy conversion efficiency had been maximized. This is because of a decrease of dangling bonds density by ESR analysis and an increase of sp2 structures by Raman analysis. When the fluorine is over certain content, the sheet resistivity increases because chain structures become larger, which is due to the CF2 bonding in F-DLC prevents ring structures. Many C2F4 species were observed and it may become precursors of the chain structure domains, such as (CF2)n.

In this study, we revealed effects of fluorine incorporation on DLC and succeeded in increasing its conductivity and improving rectification characteristics of DLC/ p-Si hetero-junction diodes. Our results indicate that DLC fluorination is effective for the semiconducting material, such as solar cell applications.

Nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films were deposited in nitrogen and hydrogen mixed gas atmospheres by coaxial arc plasma deposition (CAPD). Nitrogen-doped films with nitrogen contents of 3 and 8 at.% possessed n-type conduction. The electrical conductivity increased with increasing nitrogen content. Heterojunction diodes with p-type Si exhibited typical rectifying action. From the capacitance-voltage measurement, it was confirmed that the carrier density increases with the nitrogen content.

The use of detonation nanodiamond (DND) for drug delivery and cell-imaging is grounded on its chemical functionalization, and the key task to be addressed is the capability to simplify the process steps, to reduce the process times and to maximize the drug/ligand uptake. The idea underlying the present research is to modulate the loading capability of DND by controlled modification of the surface organic groups. To this aim the DND samples are treated either by wet chemistry, using medium-strong reducing agents, or by tunable H-plasmas produced in a custom-designed MW-RF reactor. The affinity of the treated DND surfaces for drugs has been probed by conjugating the ciproten (5,7- dimethoxycoumarin), a natural antioxidant molecule, and by testing in vitro the feasibility to use coumarin vehicled by nanodiamond (C@DND) as chemioterapeutic drug. The methodologies developed to modify the DND surfaces are offering practical solutions to the still open problems related to DND-based systems for drug delivery applications.