The critical dose for graphitization of diamond as a result of ion implantation induced damage (boron and arsenic) and subsequent thermal annealing is determined by combining secondary ion mass spectroscopy measurements, chemical etching of the graphitized layer, and TRIM simulations. Li ions are implanted as a deep marker to accurately determine the position of the graphite/diamond interface. The damage density threshold, beyond which graphitization occurs upon annealing, is found to be 1022 vacancies/cm3. This value is checked against published data and is shown to be of general nature, independent of ion species or implantation energy.

We report on a detailed analysis of the transport properties and superconducting critical temperatures of boron-doped diamond films grown along the ͕100͖ direction. The system presents a metal-insulator transition ͑MIT͒ for a boron concentration ͑n B ͒ on the order of n c ϳ 4.5ϫ 10 20 cm −3 , in excellent agreement with numerical calculations. The temperature dependence of the conductivity and Hall effect can be well described by variable range hopping for n B Ͻ n c with a characteristic hopping temperature T 0 strongly reduced due to the proximity of the MIT. All metallic samples ͑i.e., for n B Ͼ n c ͒ present a superconducting transition at low temperature. The zero-temperature conductivity 0 deduced from fits to the data above the critical temperature ͑T c ͒ using a classical quantum interference formula scales as 0 ϰ ͑n B / n c −1͒ with ϳ 1. Large T c values ͑ജ0.4 K͒ have been obtained for boron concentration down to n B / n c ϳ 1.1 and T c surprisingly mimics a ͑n B / n c −1͒ 1/2 law. Those high T c values can be explained by a slow decrease of the electron-phonon coupling parameter and a corresponding drop of the Coulomb pseudopotential * as n B → n c .

Homoepitaxial diamond layers doped with boron in the 10(20)-10(21) cm(-3) range are shown to be type II superconductors with sharp transitions (approximately 0.2 K) at temperatures increasing from 0 to 2.1 K with boron contents. The critical concentration for the onset of superconductivity in those 001-oriented single-crystalline films is about 5-7 10(20) cm(-3). The H-T phase diagram has been obtained from transport and ac-susceptibility measurements down to 300 mK.

Diamond is a unique semiconductor for the fabrication of electronic and opto-electronic devices because of its exceptional physical and chemical properties. However, a serious obstacle to the realization of diamond-based devices is the lack of n-type diamond with satisfactory electrical properties. Here we show that high-conductivity n-type diamond can be achieved by deuteration of particularly selected homo-epitaxially grown (100) boron-doped diamond layers. Deuterium diffusion through the entire boron-doped layer leads to the passivation of the boron acceptors and to the conversion from highly p-type to n-type conductivity due to the formation of shallow donors with ionization energy of 0.23 eV. Electrical conductivities as high as 2omega(-1) x cm(-1) with electron mobilities of the order of a few hundred cm2 x V(-1) x s(-1) are measured at 300 K for samples with electron concentrations of several 10(16) x cm(-3). The formation and break-up of deuterium-related complexes, due to some excess deuterium in the deuterated layer, seem to be responsible for the reversible p- to n-type conversion. To the best of our knowledge, this is the first time such an effect has been observed in an elemental semiconductor.

Homoepitaxial diamond layers grown by chemical-vapor deposition in the presence of H2S, which were published to exhibit n-type conductivity, are carefully analyzed both electrically and structurally. Hall-effect measurements as a function of temperature clearly show the samples to exhibit p-type conduction, with an activation energy, carrier concentrations, and mobilities which very much resemble those of B-doped p-type diamond. Secondary-ion-mass spectroscopy confirms that indeed the samples, previously claimed to be n type due to a donor state attributed to sulfur, contain enough unintentional boron to explain the observed p-type features.

The nitrogen vacancy color center (NV À ) in diamond is of great interest for photonic applications. Diamond nano-photonic structures are often implemented using focused-ion-beam (FIB) processing, leaving a damaged surface which has a detrimental effect on the color center luminescence. The FIB processing effect on single crystal diamond surfaces and their photonic properties is studied by time of flight secondary ion mass spectrometry and photoluminescence. Exposing the processed surface to hydrogen plasma, followed by chemical etching, drastically decreases implanted Ga concentration, resulting in a recovery of the NV À photo-emission and in a significant increase of the NV À /NV 0 ratio.

Ultrathin dielectric capping layers are a prominent route for threshold voltage control in advanced Si devices. In this work the position of an Al2O3 layer inside a HfO2-based stack is systematically varied and investigated following a low and a high temperature anneal. Electrical results are compared with a sub-nanometer resolution materials characterization, showing a diffusion of Al to the bottom HfO2 interface. A correlation is found between the presence of Al at the bottom interface and a flatband voltage increase. Based on these findings, we propose to use the position of the Al2O3 for fine-tuning the threshold voltage.

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