Ar/CH4/H2 gas mixtures have been used to deposit microcrystalline diamond, nanocrystalline diamond and ultrananocrystalline diamond films using hot filament chemical vapor deposition. A 3-dimensional computer model was used to calculate the gas phase composition for the experimental conditions at all positions within the reactor. Using the experimental and calculated data, we show that the observed film morphology, growth rate, and across-sample uniformity can be rationalized using a model based on competition between H atoms, CH3 radicals and other C1 radical species reacting with dangling bonds on the surface. Proposed formulae for growth rate and average crystal size are tested on both our own and published experimental data for Ar/CH4/H2 and conventional 1%CH4/H2 mixtures, respectively.

While absolute power levels in microelectronic devices are relatively modest (a few tens to a few hundred watts), heat fluxes can be significant (through 50 W/cm2 in current electronic chips and up to 2000 W/cm2 in semiconductor lasers). Diamond heat sinks enable heat transfer rates well above what is possible with standard thermal management devices. We have fabricated heat sinks using diamond, which has the highest temperature thermal conductivity of any known material. Polycrystalline diamonds manufactured by chemical vapor deposition (CVD) are machined by laser and combined with metallic or ceramic tiles. Cooling by fluid flow through micro-channels enhances heat removal. These unique attributes make diamond based heat sinks prime contenders for the next generation of high heat load sinks. Such devices could be utilized for efficient cooling in a variety of applications requiring high heat transfer capability, including semiconductor lasers, microprocessors, multi-chip modules in computers, laser-diode arrays, radar systems, and high-flux optics, among other applications. This paper will review test designs, heat flux measuring system, and measured heat removal values.

Double stranded desoxyribonucleic acid (ds-DNA) layers, bonded to hydrogen terminated polycrystalline diamond, are characterized by scanning electron (SEM), fluorescence (FM), and atomic force microscopy (AFM). DNA grafting has been achieved using photochemical bonding of ω-unsaturated 10-amino-dec-1-ene molecules. SEM detects local variations of electron affinities on polycrystalline diamond, revealing distinct grain structures. FM applied on fluorescence labeled ds-DNA show laterally varying intensities of typically 20 %, which resembles also grain structure as detected by SEM. Contact and tapping mode AFM characterization reveal a tilted DNA bonding to diamond, dense layer formation which gives rise to smoothening of surface properties. The lateral density variation of DNA is attributed to local variations of the photo-electron emission efficiency which affects the photochemical attachment chemistry of amine linker molecules to diamond.

Biotin was grafted onto boron doped nanocrystaline diamond electrode through a four-step-chemical process. First step of grafting was electro-chemical reduction of p-4,nitro diazonium salts. The grafting was characterized using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and fluorescence analysis. XPS analysis and curve fitting procedure lead to the identification of different bond states of carbon present in the grafted film and highlights difference of coverage rate between samples. AFM highlights the non-mononuclear aspect of the diazonium electrografting. Fluorescence measurements with avidin recognition prove the efficient of the grafting.

The behavior of diamond electrodes for electrochemical applications in aqueous media containing the protein bovine serum albumin has been explored, to examine the degree of electrode poisoning which occurs. Although the diamond electrode retains good activity in such solutions, electrode fouling is found at long contact times due to protein adsorption. Two adsorption processes are observed. The first is a simple physical adsorption mechanism, and can be simply reversed by washing the electrode in water. The second mechanism is only observed when negative potentials are applied to the diamond electrode and is attributed to the attraction and reaction of the positively charged protein at the electrode interface. Electrode poisoning is also observed in the presence of power ultrasound, although the electrochemical signals are usefully enhanced under these conditions due to enhanced mass transport to the electrode surface.

The desire to exploit the extreme properties which differentiate diamond from other, more mature wide bandgap technologies has recently been given further impetus by the development of high quality single crystal CVD diamond material [1].

To realise the significant potential of diamond devices over existing device technology depends on completing a number of key objectives, in particular providing:

(a). access in volume to high quality, ultra-high purity, single crystal material,

(b). the capability to provide carriers by doping the material in a controlled manner,

(c). the ability to process thin layers and structures.

Providing access to bulk single crystal diamond (albeit not electronic grade material) has already been largely achieved and plates are commercially available for cutting applications [2]. Routes to providing suitable charge carriers are being widely investigated. Although intrinsic diamond can have exceptional electronic properties [1], in reports of both p-type and n-type diamond [3,4] the dopants are very deep (0.37 eV and 0.6 eV for boron and phosphorous respectively), which limits the realisation of conventional electronic devices operating at ambient temperatures.

A series of novel devices undergone preliminary experimental evaluation. Devices made up of boron and intrinsic layers, where the boron concentration exceeds the limit of metallic conduction (>1×1020 cm−3), offer carrier diffusion at room temperature from the highly doped regions with low mobility, into adjacent regions of intrinsic material with high carrier mobility [5]. To provide the required device performance, the interface between the doped and intrinsic layers needs to be defect free and to change doping levels by several orders of magnitude in a few atomic layers.

Although progress over the last few years has been rapid, there remain substantial technical challenges ahead for the realisation of large scale diamond active electronics. This paper will identify and review progress against these key issues.

Due to its extreme hardness, chemical and mechanical stability, large band gap and highest thermal conductivity, poly-crystalline diamond is expected to be an excellent packaging material for biomedical and environmental MEMS devices. Recently nano crystalline diamond (NCD) has been synthesized by microwave plasma chemical vapor deposition (MPCVD) technique using a gas mixture of methane-hydrogen or methane-hydrogen and inert gas, argon mixture. Diamond synthesis from liquid carbon source has a relatively high growth rate among various CVD methods. Hot filament chemical vapor deposition (HFCVD) is popular method in order to grow the diamond particles or films. The equipment of HFCVD in present paper is simple and the easy operating. Therefore we tried to NCD synthesis by HFCVD from liquid carbon source such as methanol, ethanol etc. The structure, surface morphology, and grain size of the diamond were examined with field emission scanning electron microscopy (FE-SEM) and Raman spectroscopy. We confirmed our diamond particles as NCD with typical Raman peak of NCD. And we observed 100nm under in diameter with FE-SEM. We will refer to NCD films synthesis by HFCVD in the paper.

Diamond-like carbon (DLC) film was deposited uniformly on an irregular structure such as a polyurethane artificial heart blood pump using a special 3-dimensional type electrode. Process of applying the DLC film coating is accomplished by inserting a large number of small metallic balls (φ0.8 mm chromium balls). It is then possible to adjust the shape of the electrode in such a way that the DLC film coating can be applied to the irregular surface of the artificial heart. In investigating the availability of the electrode, under helium (He) plasma, the plasma states were measured using double probe analysis. Lateral profiles of the electron temperature were higher in the centre and decreased towards the edges of the electrode. On the other hand, the plasma density profiles were lower in the centre part than at the edges. The electrode kept ion sheath on the artificial heart blood pump's surface at self-bias voltage uniformly. The results were that the DLC film was deposited completely on the artificial heart blood pump at the film thickness of approximately 350 - 380 nm. Additionally the film structure was uniform.

This paper deals with a LT transport study in B-doped diamond. To understand the electrical transport in heavily B-doped diamond and the influence of disorder onto the electrical transport, we have prepared nanocrystalline and epitaxial B-doped diamond films at CEA Saclay. The transport properties of these layers have been studied at the Institute of Physics Czech Academy of Sciences in Prague. It has been found that our B-doped nanocrystalline diamond exhibits also the SC transition, similarly as the original Russian work done on HPHT polycrystals or single crystal diamond. Additionally, the properties of (111) epitaxial films are discussed.

The use of a chemically inert and essentially biocompatible material for cellular biosensing is an attractive idea. In this context we have studied the operation of diamond-based ion-sensitive field effect transistors (ISFETs) within solutions of varying pH, and alkali-halide concentrations. In particular, we report the use of an inexpensive diamond substrate material, often referred to as ‘black’ diamond. pH sensitivity was observed when devices based on hydrogen-terminated p-type surfaces where employed, provide some surface oxidation was performed prior to their use. Variation in the threshold voltage for ISFET operation of the order of 20mV/pH unit was determined. In terms of operation in potassium iodide solution, we have shown that the device is shows selective sensitivity to the iodide species, despite the equi-molar presence of both K+ and I- species. The origin of this selectivity is discussed.

For all its remarkable properties, diamond is well known as an interesting material for radiation detection and more particularly for medical uses. Natural diamond use for detection application is limited because of its high cost and the severe gem selection needed to fabricate reproducible and reliable devices. The recent progress of the chemical vapour deposition (CVD) technique offers new possibilities in the fabrication of ionisation chambers as well as thermoluminescent dosimeters for the particular field of radiotherapy. This paper presents the use of CVD diamond for both applications.

For the use of diamond for TL applications, the purpose of this study was to control the trapping levels in the material with deliberate incorporation of impurities in CVD diamond film during the growth.

For ionisation chamber fabrication, the aim was to purposely incorporate defects (with nitrogen incorporation) in the material in order to better understand the modification of the charge transport during irradiation. The first results obtained when the device is used to monitor the beam fluency of a medical accelerator facility are presented here.

For both applications, several preliminary dosimetric parameters were probed and namely the reproducibility of the response, the linearity of the signal with the dose, and for TL dosimeters, both the optical and thermal fadings were carefully studied. Results are extremely encouraging and lead to interesting prospects for the use of diamond for dosimetry.

Electrochemically mediated charge transfer has been primarily studied by its effect on the surface conductivity of diamond. In this paper we show that the effect is not restricted to diamond, but may occur in other material systems as well, for example, semiconducting single-walled carbon nanotubes and gallium nitride.

The growth of covalently bonded nitrophenyl layers on atomically smooth boron-doped single crystalline diamond surfaces is characterized, using cyclic voltammetric attachment and constant potential grafting by electrochemical reduction of aryl diazonium salts. We apply atomic force microscopy (AFM) to characterize nitrophenyl layer-growth and thickness. Angle-resolved X-ray photoelectron spectroscopy is applied to reveal bonding arrangement of phenyl molecules and transient current measurements during the grafting is used to investigate the dynamics of chemical bonding. Nitrophenyl groups at an initial stage of attachment grown three-dimensional forming layers with varying heights and densities. Layer thicknesses of up to 80 Å are detected for cyclic voltammetry attachment after 5 cycles, whereas the layer becomes denser and only about 25 Å thick in case of constant potential attachment. No monomolecular closed layer could be detected. The data are discussed taking into account established growth models.

We investigated the electron affinity on hydrogen-terminated nano- (NCD) and ultranano-crystalline diamond (UNCD) films to reveal influences of defects, sp2 and grain boundaries on photoemission properties. To compare properties, single crystalline IIa diamond, optical grade poly-, nano-, ultranano-crystalline diamond films, a diamond-like carbon film, a highly oriented pyrolytic graphite have been characterized. All hydrogen terminated SCD, PCD and NCD samples show continuous sub-band yield, arising at about 4.4 eV, regardless of their crystal and/or grain sizes, while UNCD, DLC, and HOPG do not show the specific photoemission in the regime hν < 6 eV. Note that the UNCD film grown with some amount of hydrogen in the gas phase (UNCD-H) shows a comparable yield spectrum as hydrogen-terminated SCD. According to the normalized spectra, obviously, the electron emission mechanism on hydrogen-terminated NCD films is the same as that of SCD with a NEA of -1.1 eV. The sub-band yield from NCD is even larger than that of SCD, which is attributed to surface enlargement.

Diamond is the ultimate candidate for heat-spreading applications because of its extreme thermal management properties. The synthesis of sub-micron diamond films is of great interest for SOD (Silicon On Diamond) wafer technology as well as for specific thermal device applications. The challenge here is the necessity to fabricate ultra-thin layers (down to 100 nm) that are continuous and homogeneous. We studied the Bias Enhanced Nucleation (BEN) pretreatment on microwave plasma reactors in order to have very high nucleation densities (> to 1011 cm−2) and optimised the following growth step of the process to obtain sub-micron covering diamond films. In this study, we focus on the bias step parameters to increase the nucleation rate and to limit the growth rate during the bias step. Then, we performed a growth step to control the morphology of the films. We obtained diamond films with thickness lower than 80 nm and with a 6 nm Root-Mean-Square roughness.

The diffusion of deuterium in boron-doped homoepitaxial diamond films leads to the passivation of boron acceptors via the formation of B-D pairs. In this letter, the stability of these complexes is investigated under the stress of a low-energy (10keV) electron-beam irradiation at low temperature (∼100K). The dissociation of the complexes is evidenced by cathodoluminescence spectroscopy and is shown to result in the reactivation of most acceptors. The dissociation yield per incident electron is found to be strongly dependent on the e-beam current, which suggests a dissociation involving a vibrational excitation of the complexes by hot electrons.

Due to its radiation harness, single crystal CVD diamond is a remarkable material for the construction of detectors used in hadron physics and for medical therapy. In this work, single crystal CVD diamond plates were grown in a microwave plasma reactor, using home design substrate holder and a relatively high pressure. Optical Emission Spectroscopy was employed during the MW-PECVD growth to characterize excited species present in the plasma and to detect the presence of residual gases such as nitrogen which is unsuitable for detector's applications.

The samples were characterized using various methods such as Raman spectroscopy, photoluminescence (PL), photocurrent spectroscopy, Raman mapping, birefringence microscopy, optical microscopy and also AFM. The best sample, exhibits a FWHM for the 1332 cm−1 Raman peak about 1.6 cm−1. Room temperature PL spectra showed no N–related luminescence, confirming the high quality of the grown single crystal diamond.

CVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One inherent problem however with diamond is the presence of defect levels that are altering the detection characteristics. They result in unstable responses and carrier losses. One of the issues can be to operate the devices in the pulsed mode regime, when transitory effects are less impacted by defective levels evolution than for steady state currents. This therefore implies the use of materials that are faster, but also of lower carrier lifetime, and therefore generally agreed to be of poorer quality. This has therefore to be compromised with respect to the desired performances.

Recent photoemission studies on heavily boron-doped superconducting diamond films, reporting the electronic structure evolution as a function of boron concentrations, are reviewed. From soft X-ray angle-resolved photoemission spectroscopy, which directly measures electronic band dispersions, depopulation of electrons (or formation of hole pockets) at the top of the valence band were clearly observed. This indicates that the holes at the top of the valence bands are responsible for the metallic properties and hence superconductivity at lower temperatures. Hard X-ray photoemission spectroscopy observed shift of the main C 1s core level and intensity evolution of a lower binding energy additional structure, suggesting chemical potential shift, carrier doping efficiency by boron doping, and possibility of boron-related cluster formations.