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Optical erbium oxide (Er 2 O 3) films were prepared by radio frequency (RF) magnetron sputtering to improve the infrared (IR) transmittance of chemical vapor deposition (CVD) diamond. This study aims to analyze the microstructure, composition and optical properties of Er 2 O 3 anti-reflection films at various oxygen/argon ratios. Atomic force microscopy (AFM) analysis was used to detect the surface morphology of chemical oxidation CVD diamond and Er 2 O 3 films. The surface roughness of Er 2 O 3 films decreased with an increase in the oxygen/argon ratio. The crystalline structure of Er 2 O 3 films was analyzed by using X-ray diffraction. Meanwhile, a gradual decrease was observed when the crystallite size and its strain were calculated. This was due to the transformation of partial phases from monoclinic to cubic structures. The chemical composition of Er 2 O 3 films was analyzed by X-ray photoelectron spectroscopy (XPS). The surface of Er 2 O 3 films underwent a transformation from the unstable structure of nonstoichiometric Er 2 O 3-x to the stable structure of Er 2 O 3 with an increase in the level of oxygen. Defect behavior was determined by transmission electron microscopy (TEM). Specifically, dislocation and twinning were observed at a high oxygen/argon ratio, which was mainly attributed to the competitive growth of polycrystalline Er 2 O 3 films. The optical constants of Ψ and △ were shifted to lower wavelengths with increase oxygen/argon ratio. The maximum transmittance of the Er 2 O 3 /diamond film was 79% in the long-wavelength infrared (LWTR) range of 8–12 μm at an oxygen/argon ratio of 1:35. This value was significantly higher than that of the high oxygen/argon ratio. The present study concludes that a low oxygen/argon ratio promotes the growth and IR transmittance of Er 2 O 3 films. [ABSTRACT FROM AUTHOR]

Diamond exhibits large application potential in the field of power electronics, owing to its excellent and desirable electronic properties. However, the main obstacles to its development originate from the small‐sized single‐crystal wafers and the instability of the electrical conductivity. This work presents a metal‐oxide‐semiconductor field‐effect transistor (MOSFET) on a diamond substrate derived from a five‐inch (110) highly preferred polycrystalline diamond film. The MOSFETs with excellent performance are fabricated by combining an H‐terminated channel and an epitaxially grown boron‐doped layer as the source/drain contacts of the diamond devices. According to the electrical statistical results of ≈110 devices on the polycrystalline diamond substrate, 44% of devices show normally‐off operation with a maximum current density of 400 mA mm−1, while 56% of devices demonstrate normally‐on operation with a maximum current density of 525 mA mm−1. The normally‐off characteristics are more related to the higher amounts of nitrogen concentration than the grain boundaries. The stable boron‐doped source and drain provide a high concentration of holes, which facilitate transport in the surface p‐type channel induced by the H‐termination. The characteristics of the MOSFETs are inspiring for the fabrication of complementary inverter circuits on large diamond wafers. [ABSTRACT FROM AUTHOR]

The fabrication of GaN-on-diamond structure by the process of diamond growth on GaN technology is becoming more and more attractive for high-power GaN devices. However, due to the high-temperature steps employed during the GaN epitaxial layer transfer process, significant stress accumulates in the GaN-on-diamond structure and induces the formation of cracks or deformations in the GaN layer. To improve the stress characteristics of the GaN layer, in this work, dual-sided diamond film deposition was carried out to accomplish the GaN-on-diamond structure. The surface morphology, interface microstructure and crystal quality of diamond on GaN were analyzed by using scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray diffraction. The results showed that the stress accumulation originating from the GaN epitaxial layer transfer process was effectively alleviated as compared with other reporteds in the literature and that the crystal quality of the GaN was only slightly altered. The stress relaxation was attributed to the low-quality diamond used as the temporary carrier during the GaN transfer process. In addition, a thin SiC transition layer in the interface is also beneficial in alleviating the mismatch between the coefficients of thermal expansion for the GaN and the diamond. [ABSTRACT FROM AUTHOR]

[Display omitted] • The La-doped Er 2 O 3 anti-reflection films was prepared by the power of magnetron sputtering. • The compound of La 2 O 3 formed along the grain boundary of the columnar crystal structure of the polycrystalline film. • The highest hardness and yield strength of the La-doped Er 2 O 3 film was two times higher than that of pure Er 2 O 3 film. • The transmittance of the La-doped Er 2 O 3 anti-reflection films only decreased 1% after erosion. The composition and microstructure consisting of anti-reflection films was obtained by the power of magnetron sputtering. X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) provided evidence to support that the doping La element exists as oxide in the grain boundaries of the matrix Er 2 O 3 films. The undoped and La-doped Er 2 O 3 films show a columnar crystal structure of the main cubic (2 2 2) plane. Twinning and a large number of dislocations show up in the undoped Er 2 O 3 films due to the competitive growth of the columnar crystal. In addition, the La-doped Er 2 O 3 films show a lower roughness (RMS) value in comparison with undoped Er 2 O 3 films. The grain size of columnar crystals decreases significantly with increasing La concentration in the La-doped Er 2 O 3 films. The fine grains resulted in the La-doped Er 2 O 3 films developing high mechanical and impact resistance properties, with an increase in hardness from 12.6 ± 2.1 GPa to 26.1 ± 3.4 GPa and the eroding area rate decreasing from 38.9 % to 1.9 %. Moreover, the La-doped Er 2 O 3 anti-reflection films on the chemical vapor deposition (CVD) diamond substrate maintained 74 % transmittance in the long-wavelength infrared range of 8–12 μm after sand eroding. [ABSTRACT FROM AUTHOR]

Diamond has attracted increasing attention because it has high thermal conductive. Here, a freestanding diamond thermal conductive film with a diameter of about 7 in. and an average thickness of 1.54 mm was prepared by DC arc plasma jet CVD with multi-stage magnetic fields. Specifically, the thickness uniformity was ensured by adding the magnetic field during the deposition of the freestanding diamond film. The morphology, structure and thermal conductivity of the diamond film were studied. The results showed that the expansion area of the DC arc plasma approached the surface of the substrate increasing duo to add the bottom magnetic field. Structural characterization revealed that the grain of the diamond film in the arc main were coarse, affected by the shape of DC arc plasma, while in the arc center and edge were fine. The main orientation of polycrystalline structure of the diamond film was the crystalline plane of (220). The Raman peaks of diamond film in different areas moved to a higher wavelength, indicating the existence of compressive stress inside the diamond film. The coarse columnar grain and a few grain boundaries were in the arc main. Therefore, the average value of the thermal conductivity (k ⊥) of diamond film measured in the arc main was 1728.9 ± 4.9 W/(m·k). Meanwhile, the thermal conductivity of the arc center and edge area was lower than that of the arc main. [Display omitted] • A freestanding diamond thermal conductive film with a diameter of about 7 in. was prepared. • DC arc plasma jet CVD with multi-stage magnetic fields was adopted. • The average value of the thermal conductivity (k ⊥) of diamond film measured in the arc main was 1728.9 ± 4.9 W/(m·k). [ABSTRACT FROM AUTHOR]

To improve the transmittance of chemical vapor deposition (CVD) diamond, erbium(III) oxide (Er 2 O 3) antireflective films were deposited on CVD diamond substrates by radio frequency (RF) magnetron sputtering. Effects of deposition temperature on structure, chemical composition and properties of the samples were investigated. A strong correlation was observed between the deposition temperature and crystalline structure evolution of the Er 2 O 3 antireflective films. With rising deposition temperature, the deposition rate, grain size and surface roughness of the Er 2 O 3 antireflective films increased. Changes of composition and chemical bonding of the films were analyzed. Results showed that the amount of bonding between Er and O atoms surface as the temperature increased. The films were structured by amorphous, monoclinic and cubic phase, with preferential orientations of C-Er 2 O 3 {222} at deposition temperature increased to 400 °C. A thickness of 10 nm transition layer was observed between the Er 2 O 3 antireflective films and the CVD diamond substrates by transmission electron microscopy (TEM). Moreover, the transition layer feature primarily consisted of Er, O and C. The hardness and modulus of Er 2 O 3 antireflective films were increased for higher deposition temperature, which positively affects the IR transmittance and adhesion strength of the Er 2 O 3 antireflective films on CVD diamond substrates. • The maximum transmittance of Er 2 O 3 /diamond sample was 80% in 7–11 μm range. • Texturization of Er 2 O 3 film interface was studied by HRTEM. • The higher deposition temperature favors crystallization of Er 2 O 3 film. • This study meets the requirements of windows for infrared (IR) imaging systems coating in the LWIR range. [ABSTRACT FROM AUTHOR]

• 21% increase of maximum transmittance of Er2O3 films deposited on diamond coatings. • Negative electrical bias induces the formation of monoclinic Er2O3 on Si(110). • Monoclinic Er2O3 effectively improve the transmittance of the diamond coating. Er 2 O 3 anti-reflection films were deposited on the surface of the chemical vapor deposited diamond films and Si(100) substrates by radio frequency magnetron sputtering. The microstructure of the Er 2 O 3 thin films and the interfacial layer were investigated by means of scanning electron microscopy, X-ray diffraction, atomic force microscopy and transmission electron microscopy. The refractive index, hardness and transmittance of the films were measured by ellipsometry, nanoindentation measurements, and Fourier transformed infrared spectroscopy. Results revealed that the bias induces the formation of a monoclinic phase and the nucleation of the Er 2 O 3 thin films is mainly observed along the (222) plane. A high-resolution TEM image revealed a 2.5-nm-thick amorphous layer at the interface between the Si substrate and Er 2 O 3 film. Notably, monoclinic Er 2 O 3 films can considerably improve the transmittance of the diamond film in the long-wavelength infrared range of 8–12 μm via the reduction of the refractive index. However, the introduction of the monoclinic phase led to the decrease of the hardness and elastic modulus of the films; hence, controlling a suitable amount of the monoclinic phase may play an extremely important role in the mechanical and optical properties of the Er 2 O 3 films. [ABSTRACT FROM AUTHOR]

Nd 2 O 3 film is a functional film with great potential application value. In this paper, thinNd 2 O 3 film was prepared on the surface of Si substrates using RF magnetron reactive sputtering. Nd 2 O 3 film with different crystal structures were controlled by changing the deposition temperature. The results show that the Nd 2 O 3 film with a cubic structure can be obtained at 150 °C, while a hexagonal structure appears at 250 °C and above. The refractive indices of the cubic and hexagonal Nd 2 O 3 films were 1.736 and 2.130, respectively. Moreover, the principle of the influence of deposition temperature on the refractive index of the film was illustrated. The hardness and the elastic modulus of the cubic Nd 2 O 3 film were 6.3 GPa and 102 GPa, respectively, which are much lower than the 9.9 GPa and 145 GPa of the hexagonal Nd 2 O 3 film. In addition, with a double-sided cubic Nd 2 O 3 film, the maximum transmittance of the diamond film reached 87.54%. The results show that the Nd 2 O 3 film is an anti-reflection film suitable for optical applications. • Nd 2 O 3 films with cubic and hexagonal structures were prepared, respectively. • The mechanical and optical properties of two kinds of Nd 2 O 3 films were compared. • Hexagonal Nd 2 O 3 film shows hardness of 9.9 GPa and elastic modulus of 145 GPa. • Diamond presents the maximum transmittance of 87.54% at 11.2 μm with Nd 2 O 3 films. [ABSTRACT FROM AUTHOR]

In this study, the effect of defects on fracture toughness in different directions was investigated. Two diamond films with a diameter of 122 mm and as-deposited thicknesses of 2.2 and 1.5 mm, respectively, were deposited by DC arc plasma jet chemical vapor deposition. To accurately obtain the fracture toughness, the films were ground and polished to 1.6 and 0.8 mm, respectively. The results indicate that many defects, including pores, are introduced into the films during the growth process, particularly on the side close to the growth surface in thicker film. The size of pores reaches micrometres, which affects the fracture toughness under loading in different directions. Due to the minimum grain size, both films exhibit a maximum toughness of 8.2 and 10.0 MPa·m1/2, respectively, with growth-surface cracks. For the thinner sample, the maximum value is followed by that of the edge-surface cracks. As the grain size of the edge surface falls between that of the growth surface and that of the nucleation surface, the results indicate that fracture toughness is affected by grain size. However, the number of pores near the growth side increases when the thickness exceeds 0.8 mm. Pores reduce the toughness, resulting in the minimum fracture toughness (6 MPa·m1/2) of the thicker diamond film with edge-surface laser cracks. The sample with an edge-surface sharp pre-crack has a similar fracture toughness of 5.6 MPa·m1/2. This study provides guidance for selecting the applied load direction. • Two thick diamond films with thicknesses 2.18 and 1.48 mm were deposited. • Fracture toughnesses of the diamond films in three directions were investigated. • Numerous pores were formed in the diamond films during orientation growth. • Due to the effect of pores, the toughness values among three directions differ. [ABSTRACT FROM AUTHOR]