Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form; however, non-planar geometries are also possible and enable a number of key applications. This paper reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, on the basis of the ability to synthesize a consistent and engineered high performance product.

https://iopscience.iop.org/article/10.1088/0953-8984/21/36/364221/pdf

Chemical vapour deposition synthetic diamond: materials, technology and applications.

Experiments on single nitrogen–vacancy (N–V) centres in diamond, which include electron spin resonance1, Rabi oscillations2, single-shot spin readout3 and two-qubit operations with a nearby13C nuclear spin4, show the potential of this spin system for solid-state quantum information processing. Moreover, N–V centre ensembles can have spin-coherence times exceeding 50 μs at room temperature5. We have developed an angle-resolved magneto-photoluminescence microscope apparatus to investigate the anisotropic electron-spin interactions of single N–V centres at room temperature. We observe negative peaks in the photoluminescence as a function of both magnetic-field magnitude and angle that are explained by coherent spin precession and anisotropic relaxation at spin-level anti-crossings. In addition, precise field alignment unmasks the resonant coupling to neighbouring ‘dark’ nitrogen spins, otherwise undetected by photoluminescence. These results demonstrate the capability of our spectroscopic technique for measuring small numbers of dark spins by means of a single bright spin under ambient conditions.

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Anisotropic interactions of a single spin and dark-spin spectroscopy in diamond

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Anisotropic Interactions of a Single Spin and Dark-Spin Spectroscopy in Diamond

The growth of monocrystalline diamond films of electronic quality and large thickness (>few hundreds of microns) is an important issue in particular for high-power electronics. In this paper, we will describe the different key parameters necessary to reach this objective. First, we will examine the deposition process and establish that only microwave assisted diamond deposition plasma reactors can achieve the optimal growth conditions for the efficient generation of the precursor species to diamond growth. Next, we will consider the influence of the monocrystalline diamond substrate orientation and quality on the growth of the epitaxial layer, especially when the deposited material thickness exceeds 100 µm. The need to use a specific pre-treatment procedure of the substrate before the growth and its impact will also be discussed. Finally we will look at the growth conditions themselves and assess the influence of the process parameters, such as the substrate temperature, the methane concentration, the microwave power density and the eventual presence of nitrogen in the gas phase, on both the morphology and quality of the films on the one hand and the growth rate on the other hand. For this, we will introduce the concept of supersaturation and comment on its evolution as a function of the process parameters.

https://iopscience.iop.org/article/10.1088/0022-3727/40/20/S04/pdf

High quality MPACVD diamond single crystal growth: high microwave power density regime

High temperature application of diamond power device

Exceptionally pure epitaxial diamond layers have been grown by microwave plasma chemical vapour deposition, which have low boron doping, from 5 × 1014 to 1 × 1016 cm−3, and the compensating n-type impurities are the lowest reported for any semiconducting diamond, 700 °C for ~1 s in air. Schottky diodes made on these epitaxial diamond films have breakdown voltages >6 kV, twelve times the highest breakdown voltage reported for any diamond diode and higher than any other semiconductor Schottky diode.

https://iopscience.iop.org/article/10.1088/0268-1242/18/3/309/pdf

Exceptionally high voltage Schottky diamond diodes and low boron doping

Epitaxial diamond with remarkably low p-type doping (1×1014–1×1017 cm−3) and exceptionally low compensation ∼1×1013 cm−3, has enabled the demonstration of a optically-switched conduction modulation of the epitaxial layer. Charge exchange between the diamond substrate and the epitaxial layer makes it possible to modulate the conductivity of the epitaxial layer. Incandescent light will make the lightly p-doped epitaxial layer insulating and ultraviolet radiation will make the layer conductive again. Once the layer conductivity has been established it will remain in the same electrical state for days, if kept in the dark.

D. D. Flechtner

Papers

Exceptionally high voltage Schottky diamond diodes and low boron doping

Optically switched conductivity of epitaxial diamond on nitrogen doped diamond substrates