Orthorhombic k-Ga2O3 thin films were grown for the first time on polycrystalline diamond free-standing substrates by metal-organic vapor phase epitaxy at a temperature of 650 °C. Structural, morphological, electrical, and photoelectronic properties of the obtained heterostructures were evaluated by optical microscopy, X-ray diffraction, current-voltage measurements, and spectral photoconductivity, respectively. Results show that a very slow cooling, performed at low pressure (100 mbar) under a controlled He flow soon after the growth process, is mandatory to improve the quality of the k-Ga2O3 epitaxial thin film, ensuring a good adhesion to the diamond substrate, an optimal morphology, and a lower density of electrically active defects. This paves the way for the future development of novel hybrid architectures for UV and ionizing radiation detection, exploiting the unique features of gallium oxide and diamond as wide-bandgap semiconductors.

Electron plasma excited by direct femtosecond laser irradiation in diamond material has been investigated using Keldysh theory. The result shows that controlling the impact ionization process is a key factor to improve laser-induced nano-micromachining.

The great demand of multifunctional portable electronic products in daily life and the need of a large integration of memories with logic devices and sensors, have increased the interest in the identification of suitable materials for neuromorphic computing applications. Major innovations in this direction have been achieved by exploring materials belonging to different fields of applications and taking advantage of already consolidated deposition methods. Despite the great interest in the field and the large use in complementary applications such as sensing electrodes, neural and cellular interfaces, the use of diamond-like materials in neuromorphic applications is still limited to a few examples. Here, the development of a synaptic element based on high-quality polycrystalline diamond layers containing Ti inclusions showing a marked and reproducible resistance switching behavior is reported. Realized by means of a hybrid chemical vapor deposition-powder flowing technique, this titanium doped diamond shows a 3D polycrystalline organization that is characterized by globular grains of a few microns. The coupling of Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses confirms the good quality of diamond phase and convincingly points out the inclusion of the titanium species within the diamond lattice.

A recent innovation in diamond technology has been the development of the "black diamond" (BD), a material with very high optical absorption generated by processing the diamond surface with a femtosecond laser. In this work, we investigate the optical behavior of the BD samples to prove a near to zero dielectric permittivity in the high electric field condition, where the Frenkel-Poole (FP) effect takes place. Zero-epsilon materials (ENZ), which represent a singularity in optical materials, are expected to lead to remarkable developments in the fields of integrated photonic devices and optical interconnections. Such a result opens the route to the development of BD-based, novel, functional photonic devices.

The following technical report discloses the results of the thermal test carried out on the single crystal diamond matrix detector prototype for the ITER Radial Neutron Camera (RNC) diagnostics system.

Integrated photonic circuits promise to be foundational for applications in quantum information and sensing technologies, through their ability to confine and manipulate light. A key role in such technologies may be played by spin-active quantum emitters, which can be used to store quantum information or as sensitive probes of the local environment. A leading candidate is the negatively charged nitrogen vacancy (NV) diamond color center, whose ground spin state can be optically read out, exhibiting long (1 ms) coherence times at room temperature. These properties have driven research toward the integration of photonic circuits in the bulk of diamond with the development of techniques allowing fabrication of optical waveguides. In particular, femtosecond laser writing has emerged as a powerful technique, capable of writing light guiding structures with 3D configurations as well as creating NV complexes. In this Perspective, the physical mechanisms behind laser fabrication in diamond will be reviewed. The properties of waveguides, single- and ensemble-NV centers, will be analyzed, together with the possibility to combine such structures in integrated photonic devices, which can find direct application in quantum information and sensing.

The absorbers method is here applied by interposing filters of variable thickness between the X-ray source and a detector so to attenuate the radiation intensity by using the attenuation coefficient as a selective photon energy operator. The analysis of the signal provided by a polycrystalline diamond thin film detector exposed to the energy-selectively-attenuated X-ray beam was used for the reconstruction of the radiation spectrum. The 50 mu m thick diamond detector achieves conditions of linear response to the dose rate of the incident radiation (linearity coefficient of 0.997 +/- 0.003) for a bias voltage >= 90 V, corresponding to an electric field >= 1.8 x 10(4) V/cm. Once the absorbers method is applied, only the detector signal linearity to dose rate allows reconstructing the source X-ray bremsstrahlung spectrum with sufficiently high accuracy.

Two-dimensional laser-induced periodic surface structures with a deep-subwavelength periodicity (80 nm ? ?/10) are obtained for the first time on diamond surfaces. The distinctive surface nanotexturing is achieved by employing a single step technique that relies on irradiation with two temporally delayed and cross-polarized femtosecond-laser pulses (100 fs duration, 800 nm wavelength, 1 kHz repetition rate) generated with a Michelson-like interferometer configuration, followed by chemical etching of surface debris. In this Letter, we demonstrate that, if the delay between two consecutive pulses is <=2 ps, the 2D periodicity of nanostructures can be tuned by controlling the number of pulses irradiating the surface. Under scanning mode, the method is effective in treating uniformly large areas of diamond, so to induce remarkable antireflection properties able to enhance the absorptance in the visible up to 50 times and to pave the route toward the creation of metasurfaces for future diamond-based optoelectronic devices.

Diamond sensors provide a promising radiation hard solution to the challenges posed by the future experiments at hadron machines. A 3D geometry with thin columnar resistive electrodes orthogonal to the diamond surface, obtained by laser nanofabrication, is expected to provide significantly better time resolution with respect to the extensively studied planar diamond sensors. We report on the development, production, and characterisation of innovative 3D diamond sensors achieving 30% improvement in both space and time resolution with respect to sensors from the previous generation. This is the first complete characterisation of the time resolution of 3D diamond sensors and combines results from tests with laser, ? rays and high energy particle beams. Plans and strategies for further improvement in the fabrication technology and readout systems are also discussed.

This article reports the first comprehensive analysis of the reliability of hydrogen-terminated diamond metal semiconductor field-effect transistors (MESFETs) submitted to OFF-state stress. We demonstrate that stress induces an increase in ON-resistance and a shift in the threshold voltage, along with a decrease in the transconductance peak value. These effects are ascribed to the generation of defects at the diamond surface and/or in the upper semiconductor layers. The defects are generated both in the access regions and under the gate, and their activation energy is 0.30 eV.

The air-exposed hydrogenated diamond surface has been studied by carrier transport measurements and density functional theory. Our results have allowed us to understand the close relationship between the physisorbed water molecules and the electrical resistance. We have therefore been able to show that the evolution of the resistance over time and temperature can be related to the extent of the hole accumulation layer originating at the surface of the hydrogenated diamond. The method has allowed us to estimate the desorption energy of a single water molecule by means of resistance measurements alone.

Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy (NV) center. The NV's ground state spin can be read out optically, exhibiting long spin coherence times of approximate to 1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhance optical interactions with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs, and microfluidics in diamond. In this Progress Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond-based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide, and microfluidics in diamond are reported, with an emphasis on integrated devices aiming toward high performance quantum sensors and quantum information systems of tomorrow.

The investigation of two different photocathodes (PCs) based on nanodiamond (ND) layers, irradiated by a KrF nanosecond excimer laser (wavelength, lambda=248 nm; photon energy, EPh=5 eV) is reported. The ND layers were deposited by means of a pulsed spray technique. Specifically, the active layer of each PC consisted of untreated (as-received) and hydrogenated ND particles, 250 nm in size, sprayed on a p-doped silicon substrate. The ND-based photocathodes were tested in a vacuum chamber at 10-6 mbar and compared to a Cu-based one, used as reference. All the photocathodes were irradiated at normal incidence. The quantum efficiency (QE) of the photocathodes was assessed. QE values of the ND-based photocathodes were higher than that of the reference one. In particular, the hydrogenated ND-based PC exhibited the highest QE due to the negative electron affinity that results from the surface terminated by hydrogen. Additionally, the photocathode surface/local temperature and the multiphoton process contribution to the electron emission were studied.

Diamond has attracted great interest in the quantum optics community thanks to its nitrogen vacancy (NV) center, a naturally occurring impurity that is responsible for the pink coloration of some diamond crystals. The NV spin state with the brighter luminescence yield can be exploited for spin readout, exhibiting millisecond spin coherence times at ambient temperature. In addition, the energy levels of the ground state triplet of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Integrated diamond photonics would be beneficial for optical magnetometry, due to the enhanced light-matter interaction and associated collection efficiency provided by waveguides, and for quantum information, by means of the optical linking of NV centers for long-range entanglement. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NV centers. Furthermore, laser written micrographitic modifications could lead to efficient and compact detectors of high energy radiation in diamond. However, it remains a challenge to fabricate optical waveguides, graphitic lines, NVs and microfluidics in diamond. In this Review, we describe a disruptive laser nanofabrication method based on femtosecond laser writing to realize a 3D micro-nano device toolkit for diamond. Femtosecond laser writing is advantageous compared to other state of the art fabrication technologies due to its versatility in forming diverse micro and nanocomponents in diamond. We describe how high quality buried optical waveguides, low roughness microfluidic channels, and on-demand NVs with excellent spectral properties can be laser formed in single-crystal diamond. We show the first integrated quantum photonic circuit in diamond consisting of an optically addressed NV for quantum information studies. The rapid progress of the field is encouraging but there are several challenges which must be met to realize future quantum technologies in diamond. We elucidate how these hurdles can be overcome using femtosecond laser fabrication, to realize both quantum computing and nanoscale magnetic field sensing devices in synthetic diamond.

Ureilites represent the second largest group of achondritic meteorites. Most ureilite fragments contain significant amounts of interstitial carbon-rich material, which is present as diamond, graphite, other graphitic compounds and hydrocarbons. In this study we investigated diamonds in three ureilitic fragments (AhS 209b, AhS 72 and NWA 7983) by scanning electron microscopy, X-ray diffraction and transmission electron microscopy with the aim to shed light on their origin. Almahata Sitta (AhS) fragments show a mixture of nanodiamond (with the presence of stacking disorder of diamond) and nanographite, while in NWA 7983 the simultaneous presence of micro- and nanodiamonds associated with nanographite was detected. Laboratory experiments (Davydov et al. 2004, 2006, 2011, 2014, 2015) demonstrated that graphite, nano-diamonds and micro-diamonds can be produced together from carbon precursors in even less than a few seconds at high pressure and high temperature like those simulating natural impact shock events. Such processes are consistent with the diamond/graphite textures observed, particularly the micro-diamond + nano-diamond assemblage in NWA 7983. Furthermore, this assemblage cannot be a product of high static pressures, which should produce micro-diamonds alone (no nano-diamonds). The results obtained in our study suggested that the origin of ureilitic diamonds is consistent with a shock event through the conversion of precursor carbon materials and not with a formation under high static pressure condition in a large planetary body (Nabiei et al. 2018). The impact event hypothesis is also supported by presence of stacking disorder of diamond, which could be formed during an asteroidal impacts event (Németh et al. 2014).

Micro-Raman spectroscopy has been used to monitor structural defects and stress state developing in 3D graphitic electrodes realized by laser irradiation for the achievement of optimized carrier collection in ionizing radiation and particle diamond detectors. Buried graphitic pillars were fabricated in a single-crystal CVD-diamond sample by means of a 400 fs pulsed laser operating at ?=1030 nm. The same conditions were also used for the realization of two series of graphitic strips on the surface allowing buried pillars connections. MicroRaman spectra of untreated regions exhibits the typical diamond peak at 1332 cm-1 which changes in intensity, width and position within the graphitic surface strips, where a G band in the range 1580-1600 cm-1 is also detected suggesting a mixed composition of the laser modified material. Strength decrease, shifting and broadening of the diamond Raman peak is detected by crossing graphitic electrodes and along buried pillars, pointing out that phase transition from diamond to graphitic carbon is accompanied both by stress development and by structural disorder in the residual diamond tissue. In these regions, Raman spectra also exhibits a broad photoluminescence background signal, whose intensity appears related to graphitization process. In particular, a splitting of the diamond Raman peak is detected around pillars on the top surfaces suggesting the occurrence of a laser-induced anisotropic stress. From these results it is then tentatively suggested that charge transport in laser modified regions occurs through both graphitic carbon and disordered diamond paths, thereby affecting the 3D carrier collection.

We investigate the effect of ultrafast laser surface machining on a monocrystalline synthetic diamond sample by means of pulsed Bessel beams. We discuss the differences of the trench-like microstructures generated in various experimental conditions, by varying the beam cone angle, the energy and pulse duration, and we present a brief comparison of the results with those obtained with the same technique on a sapphire sample. In diamond, we obtain V-shaped trenches whose surface width varies with the cone angle, and which are featured by micrometer sized channels having depths in the range of 10-20 ?m. By laser writing crossed trenches we are also able to create and tailor on the diamond surface pillar-like or tip-like microstructures potentially interesting for large surface functionalization, cells capturing and biosensing.

Laboratory experiments and seismology data have created a clear theoretical picture of the most abundant minerals that comprise the deeper parts of the Earth's mantle. Discoveries of some of these minerals in 'super-deep' diamonds-formed between two hundred and about one thousand kilometres into the lower mantle-have confirmed part of this picture1-5. A notable exception is the high-pressure perovskite-structured polymorph of calcium silicate (CaSiO3). This mineral-expected to be the fourth most abundant in the Earth-has not previously been found in nature. Being the dominant host for calcium and, owing to its accommodating crystal structure, the major sink for heat-producing elements (potassium, uranium and thorium) in the transition zone and lower mantle, it is critical to establish its presence. Here we report the discovery of the perovskite-structured polymorph of CaSiO3 in a diamond from South African Cullinan kimberlite. The mineral is intergrown with about six per cent calcium titanate (CaTiO3). The titanium-rich composition of this inclusion indicates a bulk composition consistent with derivation from basaltic oceanic crust subducted to pressures equivalent to those present at the depths of the uppermost lower mantle. The relatively 'heavy' carbon isotopic composition of the surrounding diamond, together with the pristine high-pressure CaSiO3 structure, provides evidence for the recycling of oceanic crust and surficial carbon to lower-mantle depths.

CVD-diamond represents a well-known solid state material also used for the fabrication of dosimeters applied in radiotherapy. In this field, sensitive electronics as electrometers are commonly used for signal acquisition, mainly due to a relatively low amplitude of the photocurrent produced by the dosimeter. In this paper, a compact and portable equipment able to measure currents down to the pA range is illustrated. Experimental results highlight excellent performance in terms of linearity and sensitivity in the wide investigated range (pA - nA). In addition, an in-system self-calibration mechanism is proposed to guarantee a very good system accuracy without any increase of the circuit complexity.

Double-nanotextured black diamond films with different geometries were fabricated by double-step femtosecond laser treatments at different split ratios of accumulated laser fluence. A "2D-like" pseudo-periodic nanostructure was obtained for the first time when the split ratio was slightly unbalanced in favour of the first step of the treatment, as inferred by scanning electron microscopy. Raman analysis showed that a residual biaxial stress, composed by a superposition of a tensile and a compressive component, is always present after the laser writing process, and that the two components tend to balance each other in the 2D pseudo-periodic case. Spectrophotometric measurements in the 200 e2000 nm wavelength range returned outstanding solar absorptance values for all the fabricated films (reaching the unprecedented value of 99.1% in the "2D-like" structure), launching double-nanotextured black diamond as a possible alternative to black silicon as absorbing layer for high-efficiency solar cells.