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In this article, theoretical interpretation and prediction of the optical properties of nanodiamond (ND) particles', containing various luminescence centers, was made. Particularly, nitrogen, and chromium atoms embedded into the diamond crystal lattice were modeled. In the case of nitrogen centers containing ND particles, the effect of various surface terminations (hydrogen and/or oxygen, fluorine) was also studied. To get a qualitative better understanding of the complicated and specific process of ND particles, luminescence using density functional theory, were modeled processes and states influencing the luminescence of ND particles.

We report investigation of carrier recombination and diffusivity in bulk diamonds of different crystalline structure – microcrystalline (MC) CVD‐grown and single crystalline HPHT diamonds. Presence of neutral and positively charged nitrogen and hydrogen defects was determined from NIR and UV–IR absorption spectra. Carrier injection into 1‐mm thick bulk layers was realized by two‐photon absorption at 351 nm wavelength. Carrier lifetimes of 150–330 ns in IIa type HPHT crystals correlated with Ndensity, while the lifetimes in CVD crystal exhibited very fast (80 ps), slower one (3–8 ns), and µs‐duration thermally‐activated (∼1.5 eV) decay components. The initial two components correlated with the grain size at the front and backsides of the MC diamond. Linearly increasing with injection carrier recombination rates were observed in both CVD and HPHT samples at 800 K, and fitted with effective recombination coefficient B= 3–4 × 10−9cm3/s. Ambipolar mobility and thermal diffusivity parameters in CVD and HPHT bulk crystals were measured by light‐induced free carrier and thermal grating techniques.

Nanodiamond is a novel and promising material for in vitroand in vivoimaging in living cells. In this work, we studied using quantum chemical calculation methods how the various surface terminations affect the conditions for the fluorescence of nitrogenvacancy NV centers in nanodiamond particles. We worked with clusters containing between 35 and 86 atoms of carbon containing NV centers with different charge states of their vacancies NV−and NV0 and with different terminations: OH, H, NH2, carbonyl, carboxyl, and hydroxyl groups. The systems under study were modeled by DFTbased calculations using the Gaussian 09 and Turbomole5.10 program packages.

In this work time-of-flight (TOF) measurements are performed on freestanding single crystalline (100) CVD diamond layers with different surface terminations. The transit properties and electron and hole mobility are measured for completely oxidised and completely hydrogenated diamonds. The results clearly show that the different terminations of the diamond surface have an influence on the electrical transport properties. Furthermore, evidence is given that oxygen-induced surface states influence the TOF spectra. Light emission at 235 nm and around 430 nm is observed when applying a pulsed electric field on the diamond. The small peak at 235 nm is attributed to free exciton recombination while the broad band at 430 nm is contributed to A-band luminescence. Emission spectra at voltages as high as 1.4 V/μm are given and compared. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Recent interests in freestanding single-crystal CVD diamond (SC-CVD) discs for several applications in electronics led to an intense study of SC-CVD layer growth and properties. In this work we have investigated the growth mechanism of monocrystalline CVD diamond films with surfaces smooth in nanometer scale taking into account the defect incorporation in the SC-CVD layers. Specifically we discuss the surface structure characteristics for these conditions as studied with high-resolution AFM mapping. The as-grown CVD layers were removed from the substrate by laser cutting, followed by a polishing step, yielding freestanding plates. Subsequently, microscopic and colour studies as well as infrared absorption spectroscopy were performed. These investigations revealed the presence of several characteristic defects and impurities. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In this work (100) diamond films are hydrogenated using a conventional MWPE-CVD (microwave plasma enhanced chemical vapour deposition) reactor containing a H2 or a H2/O2 mixture. For the latter, XPS (X-ray Photoelectron Spectroscopy) experiments show an increased presence of oxygen at the (sub)-surface. Contrary to pure H2-plasma treated samples, H2/O2-treated layers still posses enough conductivity to enable STS (Scanning Tunneling Spectroscopy) investigations to be carried out after an annealing at 410 °C in UHV (Ultra High Vacuum). Evidence for surface resonance states is detected, yielding a possible explanation for the measured conductivity. UPS (UV Photoelectron Spectroscopy) data point to a negative electron affinity of –0.3 eV for the H2/O2-treated layers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

By optimizing seeding techniques and plasma parameters for deposition, nanocrystalline diamond (NCD) films were deposited on different sorts of substrates with varying parameters such as temperature and methane content. Results of this optimization process were analysed by SEM, XRD, Raman, and transmission measurements. Experiments with titanium interlayers lead to a better understanding of the nucleation step and can enhance the nucleation density. This research resulted in homogeneously coalesced NCD films of less than 100 nm thickness over 3 inch Si wafers. It is also shown that it is possible to grow on different sorts of glass, using a low temperature process. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Diamond exhibits a range of outstanding properties that make it a material of interest for radiation detection and particularly in the field of dosimetry applications. In fact, its crystallographic structure makes it chemically inert and radiation hard. Moreover, its atomic number (carbon Z = 6) close to the equivalent effective atomic number of human soft tissues (Z = 7.4) and of water (reference material in radiotherapy) enables a direct evaluation of the deposited dose without requiring corrections for material nature or energy. Finally, as a bio-compatible material, it can be sterilised, and it is non-toxic thus giving strong advantages for medical uses. Natural diamonds are expensive, rare and their use implies a severe gem selection to fabricate reproducible and reliable devices. The emergence of synthetic samples from the chemical vapour deposition (CVD) technique offers new possibilities in the fabrication of ionisation chamber for the particular field of radiotherapy. Previous studies have shown that defect levels present in material clearly influence the device response under irradiation. Therefore, in order to optimise dosimetric characteristics needed in radiotherapy applications, various low and precisely nitrogen concentrations were incorporated in the material during growth. Influence of these incorporations on ionisation chamber response under medical cobalt irradiator is presented in this paper. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A biochemical method to immobilize DNA on synthetic diamond for biosensor applications is developed. Nanocrystalline diamond is grown using microwave plasma-enhanced chemical vapour deposition. On the hydrogen-terminated surface 10-undecenoic acid is tethered photochemically under 254 nm illumination, followed by 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide crosslinker-mediated attachment of amino modified DNA. The attachment is functionally confirmed by comparison of supernatant fluorescence and gel electrophoresis. The linking procedure allowed for 35 denaturation and rehybridisation steps. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Diamond films were grown in an ASTeX MW PE CVD reactor. The effect of pre-growth etching with a O2/H2 plasma and the influence of the methane concentration on growth on type Ib (100) HPHT synthetic diamonds were investigated. By controlling step flow growth we were able to prepare optical quality thick diamond films, free of hillocks and unepitaxial crystallites, with a relatively high growth rate of 4 to 5 µm/h using higher pressures and methane concentrations than standard growth conditions in combination with a modified substrate holder. All diamond films were characterized by optical microscopy, SEM, AFM and Raman spectroscopy. The mean roughness (Rms) of the films grown with a thickness of 120 µm was approximately 0.5 to 0.8 nm for scanning regions of 5 × 5 µm2. For the first time nearatomically flat films thicker than 200 µm could be prepared. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform for genetic assays and its biocompatibility opens the possibility for in vivo sensing. In this study the use of a thymidine linker for covalent DNA attachment was evaluated. Contact angle measurements provided a qualitative test of the initially oxidized surface. X-ray photoemission spectroscopy was used for further analysis of the oxides and for monitoring the effect of subsequent chemical treatments. The presence of FITC-labelled DNA was confirmed by confocal fluorescence microscopy. Enzyme linked immunosorbent assays indicated that this DNA was merely adsorbed on the diamond surface instead of covalently bound.

LYRA (the LYman-alpha RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space solar physics. A set of measurement campaigns was designed to obtain the EUV-to-VIS characterization of the diamond detectors and knowledge of their modes of operation. The outputs of this campaign provide the reference data needed for the optimization of the detectors, and for the LYRA channels definition. The measurements of responsivity in EUV and VUV spectral ranges have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The detectors spectral responsivity measurements R(λ) was done for the following wavelength ranges: 40 to 80 nm, 80 to 120 nm and 120 to 240 nm. The longer wavelength range from 210 nm to 827 nm was measured with the monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diodes exhibit high photoresponse in the deep UV region and over five orders of magnitude in discrimination between deep UV (200 nm) and visible light (550 nm). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The addition of a small amount of oxygen to the CH4 and H2 feed gas supports the diamond growth during hot filament assisted chemical vapor deposition (HFCVD) even at a substrate temperature below 500 °C. Here we present AFM, SEM, SIMS, X-ray diffraction, Raman scattering, optical transmittance spectra, PDS and temperature resolved resistivity measurements of thin B-doped CVD diamond layers deposited on silicon, fused silica and borosilicate glass at low substrate temperatures. The Raman peak 1332 cm–1 for diamond layers on silicon shifts towards lower (higher) values for layers deposited on fused silica (borosilicate glass) indicating a significant tensile (compressive) stress in diamond films deposited on amorphous substrates. Diamond films grown at low temperature are very smooth (the surface roughness below 10 nm) and they are optically transparent for photon energies up to 6 eV. However, they are highly resistive despite a relatively high B concentration in plasma during growth. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication, packaging and experimental results on the calibration of metal-semiconductor-metal (MSM) photodetectors made on diamond are reported. LYRA (Lyman-α RAdiometer onboard PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40–240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a Xe-lamp at IMO-IMOMEC. The diamond detectors exhibit a photoresponse which lie in the 35–65 mA/W range at 200 nm (corresponding to an external quantum efficiency of 20–40%) and indicate a visible rejection ratio (200–500 nm) higher than four orders of magnitude.

DC photo-conductivity and photo-Hall effect measurements were applied for the first time to measure electron transport properties of two 2–4 × 10¹⁸ cm⁻³ P-doped n-type diamonds at low temperatures down to 10 K. The low IR photosensitivity, sub-linear variation of free-electron concentration with IR light intensity as well as their freeze-out at very low temperatures were observed and explained by the presence of non-uniformly distributed defect-induced localized states (traps) in the band gap. Electron mobilities of the order of 400–500 cm²/Vs were measured at 10 K decreasing with increasing temperature as T^−1/2 to about 150–200 cm²/Vs at 300 K, in contrast to T^3/2 law expected for ionized impurity scattering. Lattice distortions extending to several nm around P atoms are discussed as possible scattering centers. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Here we present first data on P-doped polycrystalline diamond prepared by in-situ doping with phosphine. By optimisation of the growth conditions and use of polished polycrystalline CVD diamond plates we were able to incorporate P actively in the grains of polycrystalline films and to prepare n-type diamond, as confirmed by Hall measurements. We studied the P-incorporation in variously oriented grains by cathodoluminescence. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Hydrogen-terminated diamond surfaces are very attractive for devices based on surface electronics. The hole channel that governs the surface conductivity and the simplicity of the surface patterning are key features which allow a large flexibility for device design. In-plane gate field effect transistors have been fabricated with the conductive channel separated from the ohmic gate contacts by insulating thin lines, obtained by using a combination of electron beam lithography with surface oxidation. Depletion regions spreading from the highly resistive oxidized lines which separate the channel and gate regions can be controlled by applying a voltage to both lateral gate contacts. A wire structure has been designed in such a way that the gate voltage effectively modulates the conductance of the channel. The channel modulation is discussed in terms of a quasi two-dimensional surface carrier density. The effect of surface defects on the transistor properties has also been investigated. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Chemical vapour deposited (CVD) diamond is used in DNA immobilization experiments for its high stability and versatility. In this study a double-stranded, 250 base pairs long DNA fragment of the human PKU gene was covalently bound to CVD diamond films. Thymidine was used as a linker molecule for the binding in head-on configuration. The presence of surface-bound FITC-labelled DNA was confirmed by confocal fluorescence microscopy. In denaturation experiments the second, unlabelled strand of each pair was removed resulting in a loss of fluorescence. The possibility of non-specific binding of DNA to diamond can be excluded. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Diamond based surface acoustic wave (SAW) devices are extremely versatile devices that are just beginning to realize their commercial potential for use from sensors till high frequency (HF) filters for wireless telecommunications. One of the most promising piezoelectric materials for diamond based HF-SAW devices is aluminium nitride (AlN) thin film. The ability of AlN and diamond to be used for SAW applications depends both on the piezoelectric AlN layer properties and the diamond substrate properties. In this work, optimised piezoelectric (002) oriented AlN layers have been deposited on polycrystalline diamond substrates aiming at HF-SAW filter applications. CVD Polycrystalline diamond layers were deposited on silicon substrates by microwave plasma enhanced chemical vapour deposition (MW-PECVD). SAW filters with unique characteristics have been obtained due to exceptional diamond's mechanical properties [1, 2]. One of the important characteristics of CVD diamond substrate is concerns its surface roughness. Smooth diamond surfaces were obtained without polishing by a wet chemical etching of the silicon substrate at the diamond layer nucleation side. Very low surface roughness (RMS ≤1 nm) can be achieved by this technique for bias enhanced nucleated (BEN) (BEN) samples. In this paper, we report the structural characterization of the AlN films and diamond substrates by X-ray diffraction, atomic force microscopy, and transmission electron microscopy methods. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The applicability of large-area CVD diamond wafers (diameter about 5 cm, thickness about 0.1 mm), read out as thermoluminescence (TL) detectors, for assessing two-dimensional (2-D) dose distribution over their area, was investigated. To obtain 2-D TL images, a special TL reader equipped with large-area planchet and a CCD camera instead of the usual PM tube was developed. Several 2-D TL images: of an alpha source (Am-241), a Ra-226 needle source and a Ru-106 ophthalmic applicator, were measured and high-resolution digital images obtained. Our preliminary results demonstrate the potential capability of large-area CVD diamond wafers, read out as TL detectors, in 2-D dosimetry for medical applications. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Diamond is being increasingly used as a window for transmitting infra-red radiation. We show here that absorption at the important (CO2 laser) wavelength of 10.6 μm involves the simultaneous destruction and creation of phonons. Its strong temperature dependence in the range 300 K < T < 650 K is accurately described, without any adjustable parameters, in terms of three main components: the destruction of one phonon of 335 cm^–1 and the creation of a second of 1275 cm^–1; the shift to lower energy of the phonons; and a three-phonon process involving the destruction of one and the creation of two phonons. The analysis demonstrates why diamond has to be effectively cooled when used for the windows of a high-power CO2 laser.

The near-optical absorption edge photoresponse in CVD diamond thin films, prepared by the CVD method, and the photoresponse in thin boron carbo-nitride (BCN) films, prepared by the rf-inductively coupled plasma CVD technique, have been studied. In case of diamond, the subgap photoresponse is strongly influenced by surface treatments such as plasma hydrogenation or annealing. It is shown that, in case of BCN films, the gap Eg and the slope of the fundamental absorption edge depend on deposition parameters. The energy slope E0 of the Urbach tail is typically 300 meV for the nanocrystalline h-BCN films, and a typical value for Eg is about 6 eV.

The electron emission from a diamond surface is influenced by the surface termination and the surface density of states. It is known that the hydrogen termination of diamond surfaces induces p-type conduction. Scanning tunneling spectroscopy (STS), combined with high-resolution topographical imaging with the scanning tunneling microscope (STM), enables to investigate local variations in the electronic structure of surfaces. We show that the hydrogen termination is sufficient to obtain reproducible STM and STS measurements. We find that the formation of a Schottky point contact between tip and sample gives rise to a rectifying I–V characteristic. Retracting the tip results in a change in the I–V characteristics from a rectifying behavior towards normal tunneling behavior. The tunneling measurements confirm the surface p-type conductivity and Fermi level pinning at the valence band.

We used the photothermal deflection (PTD) technique working in a collinear mode to measure optical PTD maps of polished ZnSe, CVD and natural type IIa diamond optical windows at the CO2 laser wavelength (10.6 μm). This technique is sensitive to inhomogeneous absorption. The variations in PTD signal, present even in single crystal IIa diamond, agree with the interference patterns of both pump and probe laser beams. The interference pattern is discussed in detail.

In this paper we apply the quasi-steady-state photocurrent (PC) technique and photothermal ionisation spectroscopy (PTIS) at various low temperatures to study n-type P-doped CVD diamond samples, prepared under different doping conditions. The low temperature photocurrent spectra for 500 ppm P-doped films show phonon-assisted oscillatory photoconductivity with more and sharper minima than for the 1000 ppm sample. The 500 ppm PH3/CH4 doped samples exhibit at this moment also the highest reported Hall mobility at RT of 240 cm2 V–1 s–1, pointing to a better film quality with less stress, resulting in less broadening of the defect levels in the band gap. Minima in the photocurrent signal that are separated by 155 meV can be grouped. This energy corresponds to the LO phonon at the conduction band minimum, located along the Δ-axes of the diamond band structure in the [100] direction. It is created when an electron thermalises out of the conduction band into an excited level.

The quasi-parallel collinear photothermal deflection (PTD) technique was applied to the investigation of the optical absorption coefficient at the CO2laser wavelength (10.6μm) for a set of chemical vapour deposited (CVD) diamond windows of various optical qualities. The PTD measurements enabled absorption imaging to be performed and thus the mechanism of optical absorption in CVD diamond to be studied. For the measured samples, the optical absorption is affected by the black non-diamond inclusions, which are — to a greater or lesser extent, depending on the material grade — present in all CVD diamond films. The optical grade material contains just a few of these inclusions. To obtain absolute values of the optical absorption, the relative PTD values were calibrated by using a sample with known absorption (measured by laser calorimetry). The mathematical simulations were carried out using a theoretical model for the temperature (heat diffusion) profile in diamond, which yielded a very good agreement with the experimental results.

In this work we used the quasi-steady-state photocurrent method and photothermal ionisation spectroscopy (PTIS) to study the electronic structure of the P-related level in n-type phosphorus doped CVD diamond. Previously, we reported the existence of two optically active defect levels, labelled XP1and XP2, in the bandgap of these P-doped layers. XP2appeared to be only present in films showing high resistivity. Here we present a detailed PTIS and photocurrent study of the photoionisation cross-section, from liquid helium up to room temperature. At low temperatures, samples containing only the XP1defect show a phonon-induced oscillatory photoconductivity, giving information about the electronic structure of this defect. Additionally, with PTIS a sharp maximum was detected around 565meV, originating from a thermal promotion of charge carriers from an excited state of the phosphorus-related level into the conduction band. We also discuss different models for the optical ionisation cross-section of the P-related level (e.g. shallow level, deep level).

Photocurrent measurements and the Constant Photocurrent Method (CPM) were used to carry out a spectroscopic study of epitaxial phosphorus-doped n-type CVD diamond films. Two optically active defect levels, XP1 and XP2, with photoionisation energy of 0.56 and 0.81 eV, respectively, found in previous work [1] are discussed in detail here. Comparison of CPM data with the activation energy of the carriers from Hall effect measurements suggest that the XP1 defect can be attributed to the P-related donor level. XP2 remains unidentified. Measurements carried out on a set of samples show that the XP2 defect is only present in some samples showing high resistivity. To study the electronic structure of the XP1 level, photocurrent measurements at low temperatures (liquid N2 and liquid He) were done, revealing a phonon-induced oscillatory photoconductivity. Two sets of minima are observed which allow an estimation of the position of the first two excited states of phosphorus. Also a comparison is made with results from FTIR measurements.

The electronic states of boron and phosphorus in diamond have been studied by infrared absorption and photo-thermal ionisation spectroscopies. High quality boron doped synthetic diamond (p-type conductive) and phosphorus-doped CVD diamond film (n-type conductive) were used for this study. In the case of boron-doped diamond, the four main excited states of the bound hole follow a Rydberg series, suggesting that boron has a hydrogen-like behaviour, with a weak splitting of the excited states. The consistent values of the optical ionisation energy (E0 = 382 meV), of an “average” effective mass (m* = 0.74m0) and of the Bohr radius of the ground state (a* = 4.1 Å) deduced from the Rydberg series support this suggestion. The comparison with the effective mass approximation, applied for acceptor states in diamond, suggests that the top of the valence band of diamond is different from that of silicon and germanium. In the case of phosphorus-doped diamond, two excited states of the bound electron have been observed for the first time, at 523 and 562 meV from the ground level. The good agreement with the effective mass approximation suggests that phosphorus is a shallow donor, and allows us to propose a first value of the optical ionisation energy of phosphorus in diamond of about 600 meV, consistent with Hall effect measurements.

A compact electron cyclotron wave resonance (ECWR) source has been developed for the high rate deposition of hydrogenated tetrahedral amorphous carbon (ta-C:H). The ECWR provides growth rates of up to 900 Å/min over a 4″ diameter and an independent control of the deposition rate and ion energy. The ta-C:H was deposited using acetylene as the source gas and was characterized in terms of its sp3 content, mass density, intrinsic stress, hydrogen content, C–H bonding, Raman spectra, optical gap, surface roughness and friction coefficient. The results obtained indicated that the film properties were maximized at an ion energy of approximately 167 eV, corresponding to an energy per daughter carbon ion of 76 eV. The relationship between the incident ion energy and film densification was also explained in terms of the subsurface implantation of carbon ions into the growing film.

Photocurrent spectroscopy is used for studying electronic defect states in the gap of optical-quality CVD diamond. The constant photocurrent method (CPM), allowing to measure the optical (photoionization) cross-section of defects, is applied on samples with a different surface treatment. The measured photoionization cross-section spectra are discussed and attributed to main defects in CVD diamond layers. A photoionization cross-section of a defect, with an onset at about 2.2 eV, is attributed to the single-substitutional nitrogen defect (EPR P1 resonance at g = 2.0024). This defect is denoted as D2. Additionally, a defect with an onset at about 1.2 eV is observed on “as-grown” samples or after additional hydrogen plasma treatment. This defect, denoted as D1, diminishes after oxidation of the diamond sample surface. The EPR g = 2.0028 resonance, which was also suggested to be H-related, is studied as a function of hydrogenation and oxidation.

WC films are investigated for use as intermediate layers for adhesion improvement between the cemented carbide (WC-Co) substrate and a CVD diamond wear resistant layer. WC layers are prepared by reactive magnetron sputtering. Deposition conditions during the sputtering are adjusted to change the WC layer stoichiometry and the microstructure. Layers are investigated by X-ray diffraction and scanning electron microscopy (SEM) in as deposited and in annealed states. Adhesion of diamond is investigated by Rockwell-C indentation. Adhesion data shows a strong dependency on the deposition conditions for the WC layers. This data is explained in terms of Co diffusion from the substrate through the intermediate layer and of mechanical properties of the intermediate layer itself.

Ti(C,N) coatings were deposited by triode ion plating in a mixture of argon, acetylene and nitrogen. The acetylene inlet was positioned at two different locations relative to the dense plasma. The energy distribution of selected ions during Ti(CxN1-x) deposition was measured by an energy resolved mass spectrometer. The mass spectra showed wide energy distributions of Ti ions, and energy distributions of other ionized molecules, clusters and radicals. A higher probability of acetylene dissociation with the acetylene inlet directed into the plasma was observed. Preferred orientation, lattice parameters and stress for the Ti(C,N) coatings were measured by X-ray diffraction. The measured compressive stress ranged from 8 to 13 GPa, the microhardness from 0.24 to 0.27 GPa. The scratch-test revealed an adhesion comparable to that of TiN coatings.

The methods of temperature-modulated space-charge-limited currents (TM-SCLC) and post transit photocurrent analysis (PTPA) have been used to study the tail-state distribution in density of states (DOS) of p-doped a-Si:H in annealed and light soaked state. It is shown that light soaking causes an increase in the midgap DOS at about 0·50-0·55 eV accompanied by a decrease in the DOS at about 0·40-0·45 eV.

The assessment of the quality of CVD diamond films, a very important issue for the preparation of electronics-quality material, has been approached with the help of Raman, luminescence and photocurrent spectroscopy, photothermal deflection spectroscopy (PDS) and electron paramagnetic resonance (EPR). In heteroepitaxial diamond films deposited on silicon wafers by plasma-enhanced chemical vapour deposition (PECVD) we have observed the following defects: sp2 bonded carbon, carbon dangling bonds, nitrogen and silicon. Raman scattering is sensitive to sp2 bonded carbon, PDS sees total absorption due to sp2 bonded carbon, dangling bonds and nitrogen. Typically, the graphitic inclusions between the grains dominate the PDS spectrum. EPR detects carbon dangling bonds (vacancy-like defect, with possible H involvement) with g=2.0028 and paramagnetic form of nitrogen with g=2.0024. A strong photoluminescence peak at 1.68 eV reflects the Si contamination. Nitrogen-related transitions were detected by photocurrent measurement, with a characteristic threshold at about 2.1 eV, and seen in luminescence. A threshold energy of approximately 1 eV was attributed to the carbon dangling bond defect, which was observed also by EPR. This g=2.0028 signal decreases with an increase in material quality, as determined by Raman spectra.

Energy-resolved steady-state and transient photocurrent measurements are investigated with the aim to evaluate the density of states (DOS) in CVD diamond films. The steady-state photocurrent spectra reflect the photoexcitation of carriers from two dominant defect structures in CVD diamond films which we denote as D1 and D2 levels [photoexcitation onsets at about 1.0 eV (D1) and at 2.1 eV (D2)]. The comparison of the photocurrent spectra with Ib diamond allows us to attribute the D2 level to the substitutional nitrogen. The D1 level remains unidentified. The μ*τ product increases for samples showing dominantly the D1 level photoexcitation. The transient photocurrent spectra obtained after laser pulse illumination in sandwich and coplanar configurations indicate an intense interaction of excess photo-carriers with a broad distribution of the DOS.

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The cover picture on this issue of physica status solidi (a) symbolizes a diamond crystal, representing the logo of the 7th International Workshop on Surface and Bulk Defects in CVD Diamond Films, held in Diepenbeek-Hasselt, Belgium, March 13–15, 2002. This high successful series of topical workshops originated in 1996. Its proceedings are published in this journal for the fourth time. They have continously met high interest and generated remarkable citation rates (up to an impact of 5) among our readers. Topics of this year's meeting concentrated on diamond as a wide band gap semiconductor and covered surface and growth related phenomen a, doping, hydrogen, defects and their characterization as well as device applications and carbon nanotubes.