Fernando Lloret

Universidad de Cádiz | UCA · Department of Applied Physics

In this work, the successful heteroepitaxial growth of boron carbide (BxC) on 4H-SiC(0001) 4° off substrate using chemical vapor deposition (CVD) is reported. Towards this end, a two-step procedure was developed, involving the 4H-SiC substrate boridation under BCl3 precursor at 1200°C, followed by conventional CVD under BCl3 + C3H8 at 1600°C. Such...

Carbon fibre reinforced polymers (CRFP) are extensively used in many industrial applications thanks to its mechanical properties and its low weight. Nevertheless, the orthotropic character of CRFP highly reduces its applications. The transversal electrical conductivity in CRFP is two orders poorer than in the longitudinal direction. To improve thei...

One of the most efficient measures to prevent gamma radiation is shielding, which can take the form of protection barriers, storage containers, wall coating, bunkers, or many others aimed at minimizing the exposure of people to radiation. The materials used to this end have not changed much since the invention of X-rays, when materials with high at...

The effect of H⁺ implantation and annealing of diamond (100) monocrystalline substrates has been studied by ToF-SIMS, cathodoluminescence, transmission spectroscopy and TEM. Blistering conditions suitable for the Smart Cut™ technology have been identified in monocrystalline diamond, using two sets of hydrogen implantation and annealing. A first hyd...

Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility. However, it is also the one with the greatest difficulties in carrying out the...

Progress in power electronic devices is currently accepted through the use of wide bandgap materials (WBG). Among them, diamond is the material with the most promising characteristics in terms of breakdown voltage, on-resistance, thermal conductance, or carrier mobility. However, it is also the one with the greatest difficulties in carrying out the...

Doping diamond layers for electronic applications has become straightforward during the last two decades. However, dislocation generation in diamond during the microwave plasma enhanced chemical vapor deposition growth process is still not fully understood. This is a truly relevant topic to avoid for an optimal performance of any device, but, usual...

The methane concentration dependence of the plasma gas phase on surface morphology and boron incorporation in single crystal, boron-doped diamond deposition is experimentally and computationally investigated. Starting at 1%, an increase of the methane concentration results in an observable increase of the B-doping level up to 1.7×10²¹ cm⁻³, while t...

Diamond lateral growth is a powerful technique for the design and fabrication of diamond-based power electronic devices. Growth orientation affects the diamond deposition in terms of growth rate, surface roughness, and impurity incorporation. It has been shown that the finally grown surface of a patterned substrate can be predesigned based on the g...

With the aim to improve the properties of aeronautical carbon fiber reinforced polymer materials, boron‐doped diamond (BDD) has been grown on commercial carbon fibers (CF) by microwave plasma enhanced chemical vapor deposition. The growth of a BDD layer on carbon fiber is expected to increase the mechanical, electrical and thermal conductivities of...

An alternative route for the development of diamond-based technologies is the Smart-Cut process. Such a process could make possible the combination of diamond and silicon technologies, as well as building alternative structures or manufacturing large diamond wafers. However, crystalline quality and implantation-related damages may alter the electro...

Nanocrystalline diamond (NCD) field emitters have attracted significant interest for vacuum microelectronics applications. This work presents an approach to enhance the field electron emission (FEE) properties of NCD films by co-doping phosphorus (P) and nitrogen (N) using microwave plasma-enhanced chemical vapor deposition. While the methane (CH4)...

γ-alumina is a promising candidate for fabricating the gate of the diamond metal oxide semiconductor field effect transistor based on oxygen termination due to its high bandgap of 6.7 eV and high static dielectric constant of 9. Besides these properties, having a sufficient barrier for holes is mandatory to avoid carriers leakage through the gate....

With the aim to improve the properties of aeronautical carbon fibre reinforced polymer (CFRP) materials, boron-doped diamond (BDD) has been deposited on commercial carbon fibres (CF; "HexTow AS7" from Hexcel) by microwave plasma enhanced chemical vapor deposition (MWPE CVD). The deposition of BDD layer on CF is expected to increase the electrical a...

Carbon Fiber Reinforce Polymer (CFRP) are much stiffer than aerospace metallic alloys, on the other side, they have highly limited electrical and thermal conductivity. These features reduce their strength to lightnings impact, which is a strong problem for aerospace industry. The here proposed approach is to cover the carbon fibers with highly boro...

Nucleation and growth of diamond films via the CVD route is reasonably well understood, but certain questions remain. The process has long been considered a metastable process. Wang et al. showed by thermodynamic calculations that due to nanosize induced capillary rise of pressure, the CVD conditions could push the metastable growth region of diamo...

The overgrowth of {100}-oriented patterned diamond substrates by microwave plasma enhanced chemical vapor deposition (MPCVD) was studied by transmission electron microscopy (TEM) through a stratigraphic approach. A sector-like growth behavior is evidenced, resulting from a competition between slowly growing facets at protruding (top) corners and ed...

The development of new power devices taking full advantage of the potential of diamond has prompted the design of innovative 3D structures. This implies the overgrowth towards various crystallographic orientations. To understand the consequences of such growth geometries on the defects generation, a Transmission Electron Microscopy (TEM) study of o...

In contrast to Si technology, amorphous alumina cannot act as a barrier for a carrier at diamond MOSFET gates due to their comparable bandgap. Indeed, gate leaks are generally observed in diamond/alumina gates. A control of the alumina crystallinity and its lattice matching to diamond is here demonstrated to avoid such leaks. Transmission electron...

Ultimate spatial resolution in boron δ-doped homoepitaxial diamond interfaces has been achieved by diffraction contrast technique in Transmission Electron Microscopy. The combination of two reflections with the Howie-Whelan equations allows profiling the boron content of δ-doped diamond homoepitaxial layers by fitting experimentally measured CTEM i...

Epitaxial lateral growth will be required if complex diamond-based device architecture, such as, for example, Metal-oxide-semiconductor Field-effect transistors (MOSFETs) or epitaxial lateral overgrowth (ELO) substrates, need to be developed for high-power applications. To this end, undoped and doped non-planar homoepitaxial diamond were overgrown...

Alumina is a promising candidate for fabricating the gate of diamond metal oxide semiconductor field effect transistor (MOSFET) due to its outstanding nominal properties: A high gap of 8.8 eV and a high static dielectric constant of 9. However, such properties are strongly dependent on the synthesis. As gate oxides are usually very thin layers (5–5...

The objective of this work is the integration of InGaAs/GaSb/GaAs heterostructures, with high indium content, on GaAs and Si commercial wafers. The design of an interfacial misfit dislocation array, either on GaAs or Si substrates, allowed growth of strain-free devices. The growth of purposely designed superlattices with their active region free of...

In this paper, we introduce a set of experiments and analyses to comprehensively correlate the epitaxial structural defects and electrical characteristics in the pseudovertical homoepitaxial boron-doped oxygen-terminated (001) diamond metal-oxide-semiconductor capacitors (MOSCAPs). Current-voltage I(V), capacitance-voltage C(V), and capacitance-fre...

Microwave dielectric loss tangent measurements are demonstrated as a method for quantifying trace sp 2-hybridized carbon impurities in sub-micron diamond powders. Appropriate test samples are prepared by vacuum annealing at temperatures from 600 to 1200 °C to vary the sp 2 /sp 3 carbon ratio through partial surface graphitization. Microwave permitt...

Diamond lateral growth is a useful technique to assess 3D architectures of devices. The requirement of the overgrowth on etched substrates has been observed to have additional benefit in the crystallinity of the diamond. The surface roughness is enhanced and threading dislocation density is reduced as a consequence of the lateral growth on patterne...

Le diamant est le semi-conducteur par excellence pour les composants électroniques de puissance. Par conséquent, la technique de croissance du diamant et les dispositifs à base de diamant ont été largement étudiés dans le monde entier au cours des deux dernières décennies. A ce jour, les diodes Schottky à base de diamant sont les composants les plu...

Diamond is the ultimate semiconductor for power electronic devices. Consequently, diamond growth techniques and diamond-base devices have been intensively investigated over the last two decades all over the world. Among these power devices, diamond based Schottky diodes are the most advanced. However, for diamond to substitute present Si and SiC fo...

Synthetic diamond is one of the most promising materials for high power devices due to its extraordinary physical properties, such as high thermal conductivity (22 W/cm K, 4 times that of Cu), electric breakdown field (>10 MV/cm), and carrier mobility (m n =1000 cm ² /V s , m p = 2000 cm ² / V s ). Moreover, 3D architectures, i.e. lateral growth, a...

Selective diamond growth on etched diamond substrates allows the development of 3D-type device geometries, which can make possible higher capacity, higher surface for contacts and benefits from better properties versus growth orientation. Such structures need the control of lateral growth or lateral etching that guarantee the best epitaxial growth,...

The selective doped overgrowth of 3D mesa patterns and trenches has become an essential fabrication step of advanced monolithic diamond-based power devices. The methodology here proposed combines the overgrowth of plasma-etched cylindrical mesa structures with the sequential growth of doping superlattices. The latter involve thin heavily boron dope...

Heavy boron-doping layer in diamond can be responsible for the generation of extended defects during the growth processes (Blank et al., Diam. Relat. Mater. 17, 1840 (2008) [1]). As claimed recently (Alegre et al., Appl. Phys. Lett. 105, 173103 (2014) [2]), boron pair interactions rather than strain-related misfit seems to be responsible for such d...

Heavy boron doping layer in diamond is responsible in some cases of the generation of extended defects during the growth processes [1,2]. As claimed recently [3], strain related misfit seems not to be responsible for such dislocation generation but to boron pair interactions. In the present work, 3D optical and electron microscopies observations ar...

Si nanowires (NWs) have been converted to silicon-silicon carbide (Si-SiC) core-shell NWs at different conditions of substrate temperature in an ultra-high vacuum using a molecular beam epitaxy (MBE) set-up. In-situ auger electron spectroscopy (AES) and reflection high-energy electron diffraction (RHEED) allowed a control of the growth process. To...

Defects induced by boron doping in diamond layers were studied by transmission electron microscopy. The existence of a critical boron doping level above which defects are generated is reported. This level is found to be dependent on the CH₄/H₂ molar ratios and on growth directions. The critical boron concentration lied in the...

Vapor-liquid-solid (V-L-S) growth of SiC on (100) diamond substrate is reported. The crystalline quality is evaluated by transmission electron microscopy (TEM). Diffraction contrast (CTEM) observations allowed confirming the growth of fully lattice relaxed SiC 3C-type crystalline structure. Defects as dislocations at the diamond/SiC interface and s...