Boron Nitride Target Research Articles

Improving the composition and multifunctional properties of amorphous boron nitride films prepared by post-annealing assisted femtosecond pulsed laser deposition method

Amorphous boron nitride (aBN) materials have similar density to crystalline phases and retain many unique electronic properties, valuable chemical inertness and high thermal stability characteristics. However, the current research on aBN materials has mainly focused on the synthesis and electrical properties of ultrathin aBN films. In this study, we developed a post-annealing assisted femtosecond laser deposition route towards stoichiometric, continuous, and multifunctional aBN films with thickness values of ∼1 μm. A series of boron nitride films were deposited on silicon wafers using a 1030 nm, 300 fs laser with a pulse energy of ∼1 mJ and a high repetition rate of 2 kHz to ablate a hexagonal boron nitride target. The deposited films were then annealed at 900 °C in a nitrogen atmosphere. The structures and chemical compositions of these obtained films were analysed by X-ray diffraction and X-ray photoelectron spectroscopy. Fourier transform infrared and nano-scratch tests were performed to measure the infrared optical and frictional properties of the adhered films. An infrared thermal imager was used to investigate the heat-dissipation performance of these films. The results indicate the components of the aBN film are further purified, the number of large heterogeneous particles is effectively reduced, and the surface becomes smooth after post-annealing treatment. This improvement promotes the transfer of heat flux and increases the transmittance in the mid-infrared light band. The significant effect mechanisms of the post-annealing treatment on the enhancement of the composition and multifunctional properties of aBN films prepared by the femtosecond pulsed laser were provided. The uniform coverage of the aBN films on the substrates, as well as the mid-infrared optical transparency and the protective performance are highly valuable and practical for infrared window protection applications.

Surface protection of SS-316L with boron nitride based thin films using radio frequency magnetron sputtering technique

In the present work, the radio frequency (RF) magnetron sputtering process was used to develop boron nitride thin films on 316L stainless steel. The target material used in the experiment was a hexagonal boron nitride (c-BN) target. The deposition was performed in three different Ar and N2 system mixing regimes. The composition and morphology of the coating developed at various N2 and Ar plasma ratios were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The electrochemical corrosion test was used to investigate the boron nitride coating's corrosion behaviour. The goal was to study the changes in the ratio of N2 and Ar during the process and to understand the structure of cubic boron nitride (c-BN) coatings. Increased microstruc­ture uniformity and further c-BN step creation with different quantities (Q) QAr/QN2 = 2 imply a fundamental strategy for creating improved cubic boron nitride films.

In-Target Proton–Boron Nuclear Fusion Using a PW-Class Laser

Nuclear reactions between protons and boron-11 nuclei (p–B fusion) that were used to yield energetic α-particles were initiated in a plasma that was generated by the interaction between a PW-class laser operating at relativistic intensities (~3 × 1019 W/cm2) and a 0.2-mm thick boron nitride (BN) target. A high p–B fusion reaction rate and hence, a large α-particle flux was generated and measured, thanks to a proton stream accelerated at the target’s front surface. This was the first proof of principle experiment to demonstrate the efficient generation of α-particles (~1010/sr) through p–B fusion reactions using a PW-class laser in the “in-target” geometry.

Composition, dielectric breakdown, and bandgap of ultra-thin amorphous boron oxynitride produced by magnetron sputtering

Ultra-thin amorphous boron oxynitride films were deposited at room temperature on silicon and polymer substrates using radio frequency magnetron sputtering of a hexagonal boron nitride target in varied argon-nitrogen background gas ratios. The effects of nitrogen content in the sputtering gas, changes in target-to-substrate distance, and magnetron power density on the film composition were investigated with X-ray photoelectron spectroscopy and correlated to the dielectric breakdown strength and bandgap obtained from current-voltage measurements and Tauc plots. Films grown in pure Ar atmosphere at a large target-to-substrate distance displayed compositions containing metallic boron, which led to a decrease in the dielectric breakdown strength. The use of Ar:N2 mixtures and pure N2 eliminated metallic boron bonding. Decreasing the target-to-substrate distance and target power density during reactive sputtering resulted in B:N stoichiometry ratio closer to one and about 25–30 at.% oxygen. Smooth surface morphology films grown in pure N2 at a small target-to-substrate distance exhibited dielectric breakdown strength of 2.1–2.4 MV cm−1at 30 nm film thickness and bandgap of 5.4 eV. The results show the suitability of amorphous boron oxynitride for application as an insulator or gate dielectric in thin-films flexible transistors and other electronics when a low processing temperature is required.

Corrosion behavior of pulse laser deposited 2D nanostructured coating prepared by self-made h-BN target in salinity environment

Hexagonal boron nitride (h-BN) target was prepared by two step wet chemical reaction method using a nontoxic starting materials (urea and boric acid). Optimized annealing parameters (1600 °C for 2 h) and N2 environment are applied for pertinent growth of boron nitride nano powder. A mechanical procedure was acquired to convert this powder into pallet (target) for further analysis. The prepared target (white pallet) was used to fabricate the corrosion resisting h-BN nano-sheet coating using pulse laser deposition technique. A thick h-BN coating was deposited on SS 304 and Si substrates. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to characterize the coating for structural and morphological purpose. X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM), and energy-dispersive X-ray spectroscopy (EDXA) were employed to characterize the coating for surface properties and chemical composition purpose. However, Contact angle and electrochemical work station were employed for wetting and corrosion analysis tests. We find that pulsed laser deposition (PLD) grown h-BN coating shows the non-wetting (134.2°) and reduce corrosion rate by one order of magnitude compared to bare SS. On the basis of these results, the h-BN nano-sheet coating may be a promising candidate for corrosion resist application in (3.5% NaCl solution) salinity environment.

Generation of α-Particle Beams With a Multi-kJ, Peta-Watt Class Laser System

We present preliminary results on generation of energetic -particles driven by lasers. The experiment was performed at the Institute of Laser Engineering in Osaka using the short-pulse, high-intensity, high-energy, PW-class laser. The laser pulse was focused onto a thin plastic foil (pitcher) to generate a proton beam by the well-known TNSA mechanism which, in turn, was impinging onto a boron-nitride (BN) target (catcher) to generated alpha-particles as a result of proton-boron nuclear fusion events. Our results demonstrate generation of -particles with energies in the range 8-10 MeV and with a flux around 5 e9 sr-1.

Ion composition of a multicomponent beam plasma formed by electron‐beam evaporation of a boron‐containing target in medium vacuum

AbstractThin boron and boron nitride films are applied in microelectronics due to their high hardness and strength, and low electrical conductivity. However, methods for fabrication of such films are limited. One promising method is electron‐beam evaporation of a boron‐containing target to form a boron‐containing plasma. In this study, we describe our investigations of the ion mass‐to‐charge composition of the multicomponent plasma generated by heating and evaporation of boron or boron nitride targets by a continuous electron beam in a helium or nitrogen atmosphere at medium vacuum pressure (about 10 Pa). We show that at beam power sufficient for intense evaporation of the boron target, there is an increase in the mass fraction of boron ions in the plasma. For the case of evaporation of a boron nitride target, the deposited coating contains both boron and nitrogen, implying incomplete dissociation of boron nitride molecules in the evaporation process. The results of our study demonstrate the utility of electron‐beam evaporation of high melting point binary compounds in medium vacuum for coating deposition.

High-current stream of energetic α particles from laser-driven proton-boron fusion.

The nuclear reaction known as proton-boron fusion has been triggered by a subnanosecond laser system focused onto a thick boron nitride target at modest laser intensity (∼10^{16}W/cm^{2}), resulting in a record yield of generated α particles. The estimated value of α particles emitted per laser pulse is around 10^{11}, thus orders of magnitude higher than any other experimental result previously reported. The accelerated α-particle stream shows unique features in terms of kinetic energy (up to 10 MeV), pulse duration (∼10 ns), and peak current (∼2 A) at 1 m from the source, promising potential applications of such neutronless nuclear fusion reactions. We have used a beam-driven fusion scheme to explain the total number of α particles generated in the nuclear reaction. In this model, protons accelerated inside the plasma, moving forward into the bulk of the target, can interact with ^{11}B atoms, thus efficiently triggering fusion reactions. An overview of literature results obtained with different laser parameters, experimental setups, and target compositions is reported and discussed.

Microstructural characterization of BN thin films using RF magnetron sputtering method

Boron nitride films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target on 316L stainless steel substrates. Deposition process was carried out in a three different Ar and N2 mixture environment regimes. The composition and microstructure morphology of the BN films at varied mixing ratio of Ar and N2 plasma were investigated by XRD (X-Ray Diffraction) and Scanning Electron Microscopy (SEM) techniques respectively. Phase identification of c-BN was done with Fourier transform infrared spectroscopy (FTIR). The objective of the study was to investigate the effects of varying the ratio of N2 gas on the structural morphology and the formation of c-BN phase was studied. Using QAr/QN2 –5/1 ratio an improved microstructure quality and more c-BN phase formation suggesting a fundamental strategy for achieving high-quality c-BN films. The thickness of the coating was measured by calottes.

Production of intense mass separated 11C beams for PET-aided hadron therapy

A novel production system based on the Isotope Separation On-Line (ISOL) method is being developed to produce intense mass separated 11C beams for PET-aided hadron therapy. In this work, we present a systematic study of the target that was developed for optimized 11C beam production. A solid boron nitride target (BN) with approximately 21% open porosity was manufactured by spark plasma sintering to provide maximized in-target production yield with enhanced isotope release properties. Operational limitations with respect to high temperatures and oxidizing atmospheres were studied, revealing that the BN target can withstand temperatures up to 1500 °C and can be operated with a controlled O2 leak, providing O2 potentials up to −300 kJ/mol, measured at 1000 °C.

Growth and characterization of amorphous boron nitride dielectric films on Si via RF sputtering at room temperature

Good insulating amorphous boron nitride films are grown on Si substrates by radio frequency sputtering method using hexagonal boron nitride target at room temperature. Film thickness by surface profilometer, elemental composition by X-ray photoelectron spectroscopy, chemical bonding by Raman spectroscopy and morphologies by scanning electron microscopy, have been studied. The grown films are of sp2-bonded BN and verified the assumption that growth rate varies as the growth mode transition occurs. Electrical properties are elaborated via current-voltage characteristics and capacitance-voltage profiling has been studied based on metal-insulator-semiconductor (MIS) structure. Breakdown failure was evaluated to be greater than 10 MV/cm while dielectric constant was more than 3 for grown films. This exploration will support to synthesize BN at low temperature and expand its usage in electronics.

RETRACTED: Exploration of Growth Window for Phase-Pure Cubic Boron Nitride Films Prepared in a Pure N2 Plasma

Cubic boron nitride (c-BN) films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target in a pure N2 plasma. The composition and microstructure morphology of the BN films with different deposition times under pure N2 plasma or mixed Ar/N2 plasma were investigated with respect to the nucleation and growth processes. The pure-phase c-BN growth window was obtained using pure N2 gas. The effects of pure N2 gas on the growth mechanism, structural morphology, and internal compressive stress of the as-synthesized c-BN films were studied. Using pure N2 gas instead of additional Ar resulted in improved microstructure quality and much reduced compressive stress, suggesting a fundamental strategy for achieving high-quality c-BN films.

Optical and XPS studies of BCN thin films by co-sputtering of B4C and BN targets

Boron carbon nitride (BCN) thin films are investigated for their optical properties. BCN, is the unanimous choice for inter-dielectric layer (IDL) in very large scale integration (VLSI) because of its low-k dielectric constant. Optical properties can be tailored as a function of elemental composition, which makes BCN a prospective material in UV-filters and mirrors. Films are deposited by reactive co-sputtering of boroncarbide (B4C) and boronnitride (BN) with varying N2/Ar gas flow ratio by DC and RF sputtering respectively. XPS studies are performed to deduce the bonding and chemical properties of the BCN thinfilms. Optical band gap (Eg) studies are performed as a result of varying target powers, gas ratios and deposition temperatures. Eg is found to increase with N2/Ar flow ratios and deposition temperatures. BCN deposited at 20W DC exhibited higher band gap range and the highest achieved is 3.7eV at N2/Ar=0.75. Lowest value achieved is 1.9eV at N2/Ar=0.25 for as-deposited films.

Etching Studies of BCN Thin Films

The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. Recently it has been found that Boron Nitride (BN) films can achieve low-k values around and hardness comparable to diamond [1][2]. BN is hygroscopic in nature. In this respect carbon can be added to the BN structure to produce Boron Carbon Nitride (BCN) films as the possible substitute for BN. The minimum dielectric constant achieved by plasma assisted chemical vapor deposition for a BCN thin film was reported to be 1.9. [2] The BCN films are also instrumental in suppressing the Cu migration [3]. The Young’s modulus of BCN films are reported well above 20 GPa making it one of the suitable options for low-k materials [4]. In the present work, BCN films were deposited by dual target sputtering of boron carbide (BC) target (DC), boron nitride (BN) target (RF) in nitrogen ambient with argon. The films were deposited under various N­2/Ar gas flow ratios and temperature. BCN is etched using an etchant that consists of 16 parts of Phosphoric acid (H3PO4), 1 part of Nitric acid (HNO3), 1 part of Acetic acid (CH3COOH), 20 parts of DI water. Various plots of etch rates with respect to deposition parameters and Arrhenius plots are studied. REFERENCES [1] Jun Liu, Kian Ping Loh, Ming Lin, Yong Lim Foo, Wei De Wang, and Dong Zhi Ch, Journal of Applied Physics, 96 (2004) 6679. [2] Riedel R., Advanced Materials, 4 (1992) 759. [3] M. K Mazumder, R. Moriyama, D. Watanabe, C. Kimura, H. Aoki, and T. Sugino: Jpn. J. Appl. Phys. 46 (2007) 2006. [4] C. Morant, D. Caceres, J. M. Sanz, and E. Elizalde: Diamond Relat. Mater. 16 (2007) 1441.

XPS and FTIR Studies of Dual Target Sputtered Bcn Thin Films

The ever increasing advancements in semiconductor technology and continuous scaling of CMOS devices mandate the need for new dielectric materials with low-k values. The interconnect delay can be reduced not only by the resistance of the conductor but also by decreasing the capacitance of dielectric layer. Also cross-talk is a major issue faced by semiconductor industry due to high value of k of the inter-dielectric layer (IDL) in a multilevel wiring scheme in Si ultra large scale integrated circuit (ULSI) devices. Recently it has been found that Boron Nitride (BN) films can achieve low-k values around and hardness comparable to diamond [1][2]. BN is hygroscopic in nature. In this respect carbon can be added to the BN structure to produce Boron Carbon Nitride (BCN) films as the possible substitute for BN. The minimum dielectric constant achieved by plasma assisted chemical vapor deposition for a BCN thin film was reported to be 1.9. [2] The BCN films are also instrumental in suppressing the Cu migration [3]. The Young’s modulus of BCN films are reported well above 20 GPa making it one of the suitable options for low-k materials [4]. In the present work, BCN films were deposited by dual target sputtering of boron carbide (BC) target (DC), boron nitride (BN) target (RF) in nitrogen ambient with argon. The films were deposited under various N­2/Ar gas flow ratios and temperature. XPS and FTIR measurements were performed to find the relative chemical compositions, chemical bonds and behavior of the deposited films with respect to change in N­2/Ar gas flow ratios and deposition temperature. REFERENCES [1] Jun Liu, Kian Ping Loh, Ming Lin, Yong Lim Foo, Wei De Wang, and Dong Zhi Ch, Journal of Applied Physics, 96 (2004) 6679. [2] Riedel R., Advanced Materials, 4 (1992) 759. [3] M. K Mazumder, R. Moriyama, D. Watanabe, C. Kimura, H. Aoki, and T. Sugino: Jpn. J. Appl. Phys. 46 (2007) 2006. [4] C. Morant, D. Caceres, J. M. Sanz, and E. Elizalde: Diamond Relat. Mater. 16 (2007) 1441.

Temporally and spatially resolved plasma spectroscopy in pulsed laser deposition of ultra-thin boron nitride films

Physical vapor deposition (PVD) has recently been investigated as a viable, alternative growth technique for two-dimensional materials with multiple benefits over other vapor deposition synthesis methods. The high kinetic energies and chemical reactivities of the condensing species formed from PVD processes can facilitate growth over large areas and at reduced substrate temperatures. In this study, chemistry, kinetic energies, time of flight data, and spatial distributions within a PVD plasma plume ablated from a boron nitride (BN) target by a KrF laser at different pressures of nitrogen gas were investigated. Time resolved spectroscopy and wavelength specific imaging were used to identify and track atomic neutral and ionized species including B+, B*, N+, N*, and molecular species including N2*, N2+, and BN. Formation and decay of these species formed both from ablation of the target and from interactions with the background gas were investigated and provided insights into fundamental growth mechanisms of continuous, amorphous boron nitride thin films. The correlation of the plasma diagnostic results with film chemical composition and thickness uniformity studies helped to identify that a predominant mechanism for BN film formation is condensation surface recombination of boron ions and neutral atomic nitrogen species. These species arrive nearly simultaneously to the substrate location, and BN formation occurs microseconds before arrival of majority of N+ ions generated by plume collisions with background molecular nitrogen. The energetic nature and extended dwelling time of incident N+ ions at the substrate location was found to negatively impact resulting BN film stoichiometry and thickness. Growth of stoichiometric films was optimized at enriched concentrations of ionized boron and neutral atomic nitrogen in plasma near the condensation surface, providing few nanometer thick films with 1:1 BN stoichiometry and good thicknesses uniformity over macroscopic areas.

Effect of deposition temperature on cubic boron nitride thin film deposited by unbalanced magnetron sputtering method with a nanocrystalline diamond buffer layer

Cubic boron nitride (c-BN) films were deposited by the unbalanced magnetron sputtering method. A Si substrates coated with a nanocrystalline diamond (NCD) was used as a substrate. The deposition temperature was varied systematically from room temperature to 800 °C. A boron nitride target was used which was connected to a radio frequency power supply at 400 W. High frequency power connected to a substrate holder was used for self-biasing. The c-BN phase forms for all samples, irrespective of the deposition temperature, with a little amount of hexagonal phase existing as an intrinsic turbostratic boron nitride (t-BN) layer, whose thickness decreased with increasing temperature. The residual stress was maintained at a nearly constant compressive value. The adhesion improved markedly at high deposition temperature, but the insertion of the NCD buffer layer was ineffective in inhibiting the formation of t-BN layer under the present deposition condition.

Effect of radio-frequency electric power applied to a boron nitride unbalanced magnetron sputter target on the deposition of cubic boron nitride thin film

Cubic boron nitride (c-BN) films were deposited by an unbalanced magnetron sputtering method. A (100) Si wafer with a nanocrystalline diamond thin film as a surface coating layer or that without it was used as a substrate. The target power was varied from 100 to 400 W. A boron nitride target was used, which was connected to a radio frequency power supply. High frequency power connected to a substrate holder was used for self-biasing. The deposition pressure was 0.27 MPa with a flow of Ar (18 sccm) — N2 (2 sccm) mixed gas. The existence of threshold bias voltages for c-BN formation and resputtering were observed irrespective of target power. The bias voltage window for c-BN formation broadened with increased target power. The deposition rate decreased with enhanced bias voltage and decreased target power. Residual stresses of the films did not vary noticeably with target power within the target power range of c-BN formation. A parameter space for c-BN formation according to the target power and the bias voltage, as two variables, was suggested.

Study the gas sensing properties of boron nitride nanosheets

In the present communication, we report on the synthesis of boron nitride nanosheets (BNNSs) and study of their gas sensing properties. BNNSs are synthesized by irradiating pyrolytic hexagonal boron nitride (h-BN) target using CO2 laser pulses. High resolution transmission electron microscopic measurements (HRTEM) revealed 2-dientional honeycomb crystal lattice structure of BNNSs. HRTEM, electron diffraction, XRD and Raman scattering measurements clearly identified h-BN. Gas sensing properties of synthesized BNNSs were analyzed with prototype gas sensor using methane as working gas. A systematic response curve of the sensor is recorded in each cycle of gas “in” and “out”; suggesting excellent sensitivity and high performance of BNNSs-based gas-sensor.

The parameter space of hydrogen content added to Ar–nitrogen sputtering gas and substrate bias voltage for the formation of cubic boron nitride thin film deposited by unbalanced magnetron sputtering method

The parameter space for the formation of cubic phase of boron nitride thin films as a function of substrate bias voltage and hydrogen content added to Ar–N2 reactive sputtering gas was proposed. Cubic boron nitride (c-BN) films were deposited by unbalanced magnetron sputtering (UBM) method. Thin (100μm) Si strips (3×40mm2) were used as substrates. A boron nitride target was used, which was connected to a radio frequency (RF) power supply set at 400W. High frequency power connected to a substrate holder was used for self-biasing of up to −110V. The deposition pressure was 0.27Pa with a flow of Ar (18sccm) — N2 (2sccm) mixed gas irrespective of hydrogen addition. Hydrogen gas up to 16sccm was added to the Ar–N2 mixed gas. The addition of hydrogen tended to decrease the threshold substrate bias voltage for c-BN formation. Even under low bias voltage, where only hexagonal boron nitride (h-BN) formed under the Ar–N2 gas atmosphere, c-BN began to form with the addition of hydrogen to the gas. The surface of the film was very flat irrespective of the amount of added hydrogen. The deposition rate reduced with increasing hydrogen content. The residual stress decreased to 2GPa with a hydrogen flow of 10sccm, while maintaining the c-BN fraction in the film above 60%. The role of the hydrogen during the c-BN formation was briefly discussed.