Diamond is not only the hardest material in nature, but is also an extreme electronic material with an ultrawide bandgap, exceptional carrier mobilities, and thermal conductivity. Straining diamond can push such extreme figures of merit for device applications. We microfabricated single-crystalline diamond bridge structures with ~1 micrometer length by ~100 nanometer width and achieved sample-wide uniform elastic strains under uniaxial tensile loading along the [100], [101], and [111] directions at room temperature. We also demonstrated deep elastic straining of diamond microbridge arrays. The ultralarge, highly controllable elastic strains can fundamentally change the bulk band structures of diamond, including a substantial calculated bandgap reduction as much as ~2 electron volts. Our demonstration highlights the immense application potential of deep elastic strain engineering for photonics, electronics, and quantum information technologies.Copyright © 2021, American Association for the Advancement of Science.

Though the complementary power field effect transistors (FETs), e.g., metal-oxide-semiconductor-FETs (MOSFETs) based on wide bandgap materials, enable low switching losses and on-resistance, p-channel FETs are not feasible in any wide bandgap material other than diamond. In this paper, we propose the first work to investigate the impact of fixed positive surface charge density on achieving normally-off and controlling threshold voltage operation obtained on p-channel two-dimensional hole gas (2DHG) hydrogen-terminated (C-H) diamond FET using nitrogen doping in the diamond substrate. In general, a p-channel diamond MOSFET demonstrates the normally-on operation, but the normally-off operation is also a critical requirement of the feasible electronic power devices in terms of safety operation. The characteristics of the C-H diamond MOSFET have been analyzed with the two demonstrated charge sheet models using the two-dimensional Silvaco Atlas TCAD. It shows that the fixed-Fermi level in the bulk diamond is 1.7 eV (donor level) from the conduction band minimum.  However, the upward band bending has been obtained at AlO/SiO/C-H diamond interface indicating the presence of inversion layer without gate voltage. The fixed negative charge model exhibits a strong inversion layer for normally-on FET operation, while the fixed positive charge model shows a weak inversion for normally-off operation.  The maximum current density of a fixed positive interface charge model of the AlO/C-H diamond device is - 290 mA/mm, which corresponds to that of expermental result of AlO/SiO/C-H diamond - 305 mA/mm at a gate-source voltage of - 40 V. Also, the threshold voltage V is relatively high at V = - 3.5 V, i.e., the positive charge model can reproduce the normally-off operation. Moreover, we also demonstrate that the V and transconductance g correspond to those of the experimental work.© 2022. The Author(s).

The seeding for large-area mosaic diamond films approaching single-crystal quality is described. The technique includes patterned etching of relief structures in Si substrates, deposition from a slurry and orientation of macroscopic diamond seed crystals in the structures, and chemical vapor deposition overgrowth of the diamond seeds to form a continuous film. The film comprises ∼100 μm single crystals, which are separated by low-angle grain boundaries of a few degrees or less. We believe that these low-angle grain boundaries will not affect the electrical properties of majority-carrier devices.

We synthesized a mosaic diamond wafer 2 in. in size (40 × 60 mm2), which consisted of 24 single-crystal diamond (SCD) plates 10 × 10 mm2 in area, by using microwave plasma chemical vapor deposition. Even by using a cloning technique, cracking frequently occurred and the non-uniformity was remarkable for wafers that were larger than 1 in. in size. This has not been observed in smaller samples before. Appropriate crystallographic directions could avoid the cracking and is one of the predominant factors in fabricating large area SCD wafers. Comparison with numerical simulations highlighted the importance of uniformity of the substrate temperature distribution on the uniformity of the growth.

This paper reports the results of high-pressure high-temperature (HPHT) diamonds growing in an Fe–C melt with introduction of 1 wt% sulfur.

It is shown that diamond nucleation on iridium buffer layers followed by an appropriate textured-growth step offers a viable way to realize single-crystal diamond films. Bias-enhanced nucleation on iridium layers results in heteroepitaxial diamond films with highly improved alignment. By a subsequent textured-growth step, the mosaicity can be further reduced for tilt as well as for twist in sharp contrast to former experiments using silicon substrates. Minimum values of 0.17° and 0.38° have been measured for tilt and twist, respectively. Plan view transmission electron microscopy of these films shows that, for low thicknesses (0.6 μm and 8 μm), the films are polycrystalline, consisting of a closed network of grain boundaries. In contrast, at the highest thickness (34 μm) most of the remaining structural defects are concentrated in bands of limited extension. The absence of an interconnected network of grain boundaries shows that the latter films are no longer polycrystalline.

A detailed mechanism for heteroepitaxial diamond nucleation under ion bombardment in a microwave plasma enhanced chemical vapour deposition setup on the single crystal surface of iridium is presented. The novel mechanism of Ion Bombardment Induced Buried Lateral Growth (IBI- BLG) is based on the ion bombardment induced formation and lateral spread of epitaxial diamond within a -1 nm thick carbon layer. Starting from one single primary nucleation event the buried epitaxial island can expand laterally over distances of several microns. During this epitaxial lateral growth typically thousands of isolated secondary nuclei are generated continuously. The unique process is so far only observed on iridium surfaces. It is shown that a diamond single crystal with a diameter of -90 mm and a weight of 155 carat can be grown from such a carbon film which initially consisted of 2. 10(13) individual grains.

Diamond films grown on {100}, {111} boron-terminated, and nitrogen-terminated facets of cubic boron nitride (c-BN) single crystals were characterized by Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The evolution of morphology and microstructure of the diamond films at different stages during the growth process were followed by SEM investigation. The results indicate that diamond growth proceeds by nucleation of oriented three-dimensional islands followed by their coalescence. Cross-sectional TEM specimens were prepared from thick (over 10 μm) continuous diamond films grown on {111} boron-terminated surfaces. Selected-area diffraction and high resolution TEM images show that the diamond film has a parallel orientation relationship with respect to the substrate. Characteristic defects, common to diamond films obtained by chemical vapor deposition on other substrates, are also discussed.

A highly (111)-oriented, highly coalesced diamond film was grown on platinum (111) surface by microwave plasma chemical vapor deposition (MPCVD). Scanning electron microscopy and x-ray diffraction analyses revealed that the (111) diamond facets were azimuthally oriented epitaxially with respect to the orientation of the Pt(111) domain underneath, with the neighboring facets of diamond being coalesced with each other. The film was confirmed as diamond using Raman spectroscopy.

The parameter space for the heteroepitaxial nucleation of diamond on Si(001) using the bias process was studied by x-ray diffraction texture measurements. It was found that heteroepitaxial orientation can be achieved over a wide range of different parameters provided that the bias time is within a definite time interval. It was observed that twidth, the width of the time window, and topt , the bias time for optimal azimuthal alignment, strongly decrease with the absolute value of the bias voltage. For high bias voltages an extremely low value of topt (20 s at −300 V) was found. Applying the bias conditions longer than topt resulted in a strong decrease of the pole density maxima of the heteroepitaxial grains accompanied by a significant broadening of their azimuthal distribution that is interpreted in terms of two different routes for the loss of epitaxy. The different time constants characterizing the process window for a fixed bias voltage are traced back to feedback of the growing film on the plasma and on the electrical field distribution above the substrate.

\n Epitaxial growth of diamond on iridium thin films was performed by direct-current plasma chemical vapor deposition with ion irradiation pretreatment of the substrate. Pyramidal epitaxial diamond particles with a number density of ∼108 cm-2 were grown on the iridium film. The epitaxial relation is written as (100) diamond//(100) iridium and [001] diamond//[001] iridium. Tilting of the epitaxial relation, as occasionally observed for diamond on silicon or beta silicon carbide, is scarcely observed. Erosion,as observed for diamond on nickel substrates, is not observed. The effect of the ion irradiation of the substrate is discussed briefly. \n

In this work, hydrogen-terminated diamond (H-diamond) metal-oxide-semiconductor field-effect-transistors (MOSFETs) on a heteroepitaxial diamond substrate with an Al2O3 dielectric and a passivation layer were characterized. The full-width at half maximum value of the diamond (004) X-ray rocking curve was 205.9 arcsec. The maximum output current density and transconductance of the MOSFET were 172 mA/mm and 10.4 mS/mm, respectively. The effect of a low-temperature annealing process on electrical properties was also investigated. After the annealing process in N2 atmosphere, the threshold voltage (Vth) and flat-band voltage (VFB) shifts to negative direction due to loss of negative charges. After annealing at 423 K for 3 min, the maximum value of hole field effective mobility (μeff) increases by 27% at Vth − VGS = 2 V. The results, which are not inferior to those based on homoepitaxial diamond, promote the application of heteroepitaxial diamond in the field of electronic devices.

One-inch free-standing (001) diamond layers on a (112¯0) (a-plane) sapphire substrate with an Ir buffer layer (Kenzan Diamond®) were grown. The full-width at half maximum values of (004) and (311) x-ray rocking curves were 113.4 and 234.0 arc sec, respectively. The dislocation density of the substrates was 1.4 × 107 cm−2, determined by plan-view transmission electron microscopy observation. These values are much lower than the reported values among heteroepitaxial diamonds. Furthermore, x-ray pole figure measurements showed four symmetry of the crystal, showing single crystallinity without any twinning. The curvature radius of diamond was measured to be 90.6 cm, which is much larger than previous values, ca. 20 cm. Surprisingly, a cubic-lattice (001) diamond crystal was epitaxially grown on a trigonal-lattice (112¯0) sapphire substrate. However, we found that the epitaxial relation is diamond (001) [110]//Ir (001) [110]//sapphire (112¯0) [0001]. Now, high-quality one-inch diamond wafers will be available as a substrate used for diamond electronic devices.

The development of dislocation density and micro-strain in heteroepitaxial diamond films on iridium was measured over more than two decades of thickness up to d ≈ 1 mm. Simple mathematical scaling laws were derived for the decrease of dislocation density with increasing film thickness and for its correlation with micro-strain. The Raman line width as a measure of micro-strain showed a huge decrease to 1.86 cm−1, close to the value of perfect single crystals. The charge collection properties of particle detectors built from this material yield efficiencies higher than 90% in the hole-drift mode, approaching the performance of homoepitaxial films.

The present study shows that the heteroepitaxial growth of diamond by chemical vapour deposition (CVD) on Ir/YSZ/Si(111) substrates with off-axis angles of few degrees can generate intrinsic stress with huge anisotropy of several GPa in the diamond films. For all investigated off-axis directions and angles, a plane stress state with a perpendicular component σ33 ∼ 0 GPa is derived by X-ray diffraction. The size and direction of the associated in-plane stress tensor components exhibit a unique dependency on the off-axis tilt direction. They can combine the simultaneous presence of tensile and compressive stress within a layer. Stress anisotropy increases with the off-axis angle. For diamond with off-axis tilt towards [110] and [112], the principal axes of the tensor are parallel and perpendicular, respectively, to the projection of the off-axis direction into the film plane, whereas for [11¯0] they are rotated by an angle of ∼30°. For a consistent explanation of this complex behaviour, it is suggested that the measured stress is generated by the combined action of growth parameter controlled effective climb of dislocations and off-axis growth induced dislocation tilting. It is supposed that the described mechanism is not only valid for diamond CVD but also contributes to anisotropic stress formation in other semiconductor materials grown on vicinal surfaces.

In the present study, systematic correlations were revealed between the propagation direction of threading dislocations, the off-axis growth conditions, and the stress state of heteroepitaxial diamond on Ir/YSZ/Si(111). Measurements of the strain tensor ε⃡ by X-ray diffraction and the subsequent calculation of the tensor of intrinsic stress σ⃡ showed stress-free samples as well as symmetric biaxial stress states for on-axis samples. Transmission electron microscopy (TEM) lamellas were prepared for plan-view studies along the [1¯1¯1¯] direction and for cross-section investigations along the [112¯] and [11¯0] zone axes. For samples grown on-axis with parameters which avoid the formation of intrinsic stress, the majority of dislocations have line vectors clearly aligned along [111]. A sudden change to conditions that promote stress formation is correlated with an abrupt bending of the dislocations away from [111]. This behaviour is in nice agreement with the predictions of a model that attributes formation of intrinsic stress to an effective climb of dislocations. Further growth experiments under off-axis conditions revealed the generation of stress states with pronounced in-plane anisotropy of several Gigapascal. Their formation is attributed to the combined action of two basic processes, i.e., the step flow driven dislocation tilting and the temperature dependent effective climb of dislocations. Again, our interpretation is supported by the dislocation propagation derived from TEM observations.

The synthesis of heteroepitaxial monocrystalline diamond films has been of technological and scientific interest for several decades. Using chemical vapor deposition techniques, polycrystalline diamond has been successfully grown on many substrates. However, iridium emerges in providing highly oriented films, significantly better than any other transition metals. In the present work we propose an ab initio density functional study of the interaction of diamond with different substrates used experimentally. The origin of iridium’s specific behavior is investigated. The kinetics of carbon atoms in the substrate lattice is found to play a key role, determining the nucleation mechanisms and hence the quality of the final diamond film.

Two dimensional (2D) materials consist of one to a few atomic layers, where the intra-layer atoms are chemically bonded and the atomic layers are weakly bonded. The high bonding anisotropicity in 2D materials make their growth on a substrate substantially different from the conventional thin film growth. Here, we proposed a general theoretical framework for the epitaxial growth of a 2D material on an arbitrary substrate. Our extensive density functional theory (DFT) calculations show that the propagating edge of a 2D material tends to align along a high symmetry direction of the substrate and, as a conclusion, the interplay between the symmetries of the 2D material and the substrate plays a critical role in the epitaxial growth of the 2D material. Based on our results, we have outlined that orientational uniformity of 2D material islands on a substrate can be realized only if the symmetry group of the substrate is a subgroup of that of the 2D material. Our predictions are in perfect agreement with most experimental observations on 2D materials' growth on various substrates known up to now. We believe that this general guideline will lead to the large-scale synthesis of wafer-scale single crystals of various 2D materials in the near future.

Van Luan Nguyen; Shin, Bong Gyu; Dinh Loc Duong; Kim, Sung Tae; Perello, David; Chae, Sang Hoon; Quoc An Vu; Lee, Young Hee Sungkyunkwan Univ, Inst Basic Sci, IBS Ctr Integrated Nanostruct Phys, Suwon 440746, South Korea. Van Luan Nguyen; Kim, Sung Tae; Quoc An Vu; Lee, Young Hee Sungkyunkwan Univ, Dept Phys, Dept Energy Sci, Suwon 440746, South Korea. Lim, Young Jin; Lee, Seung Hee Chonbuk Natl Univ, Dept BIN Fus Technol, Jeonju 561756, Jeonbuk, South Korea. Lim, Young Jin; Lee, Seung Hee Chonbuk Natl Univ, Dept Polymer Nano Sci & Technol, Jeonju 561756, Jeonbuk, South Korea. Yuan, Qing Hong E China Normal Univ, Dept Phys, Shanghai 200062, Peoples R China. Ding, Feng Hong Kong Polytech Univ, Inst Text & Clothing, Kowloon, Hong Kong, Peoples R China. Jeong, Hu Young Ulsan Natl Inst Sci & Technol, Cent Res Facil, Ulsan 689798, South Korea. Shin, Hyeon Suk Ulsan Natl Inst Sci & Technol, Low Dimens Carbon Mat Ctr, Interdisciplinary Sch Green Energy, Ulsan 689805, South Korea. Shin, Hyeon Suk Ulsan Natl Inst Sci & Technol, Sch Mech & Adv Mat Engn, Ulsan 689805, South Korea. Lee, Seung Mi Korea Res Inst Stand & Sci, Ctr Nanomat Characterizat, Taejon 305340, South Korea.

A competition between diamond nucleation and growth is proposed in which the surface and bulk nucleation coexist and compete.

A model for diamond nucleation by energetic species (for example, bias-enhanced nucleation) is proposed. It involves spontaneous bulk nucleation of a diamond embryo cluster in a dense, amorphous carbon hydrogenated matrix; stabilization of the cluster by favorable boundary conditions of nucleation sites and hydrogen termination; and ion bombardment-induced growth through a preferential displacement mechanism. The model is substantiated by density functional tight-binding molecular dynamics simulations and an experimental study of the structure of bias-enhanced and ion beam-nucleated films. The model is also applicable to the nucleation of other materials by energetic species, such as cubic boron nitride.