Deposited Boron Nitride Research Articles

Energy storage performances of polymer-based composite dielectrics containing an in-situ-grown boron nitride layer

Polymer-based energy storage materials are widely utilized in the fields of electrical and electronics due to their high-power density and excellent charge-discharge efficiency. In this study, polyetherimide (PEI) composite films with outstanding energy storage properties were prepared by growing an inorganic barrier layer of boron nitride (BN) on the surface of PEI films through the in situ chemical vapor deposition (PECVD) method. The effects of BN deposition time on the dielectric properties, leakage current density, and energy storage properties of the composite films were investigated. The results reveal that the BN inorganic barrier layer, prepared by the PECVD method, demonstrates excellent interfacial compatibility with the PEI polymer matrix and forms a densely deposited layer. The BN inorganic barrier layer effectively suppresses carrier injection at the electrode, reduces the current density inside the PEI composite film, and improves the breakdown strength of the composite film. The composite film exhibits optimal performance when BN is deposited for 20 min. At an electric field strength of 660 MV/m, the energy storage density of the composite film reaches 6.08 J/cm3, which is 1.53 J/cm3 higher than that of pure PEI, while maintaining a charge-discharge efficiency of 90.43%. The findings of this study provide valuable theoretical support for the design of polymer-based energy storage materials.

Calculating the penetration depth of reaction in chemical gas-phase deposition of boron nitride within porous bodies

The thermodynamic calculations conducted using the TERRA software package for the B–Cl–N–H system revealed that the inclusion of hydrogen into the B–Cl system significantly diminishes the thermodynamic stability of BCl3 with the possibility of boron formation in the condensed phase. On the other hand, the introduction of ammonia, which includes hydrogen, results in the synthesis of boron nitride across a broad temperature spectrum. The analysis of kinetic relationships uncovered three distinct regions in the boron nitride deposition process: K – kinetic region (up to 1400 K), D – diffusion region (above 1800 K) and T – transition region. The activation energy for the kinetic region was calculated as Ea = 134 kJ/mol. Within the temperature range of 1023–1123 K, linear dependences were observed. The computation of the penetration depth for the boron nitride deposition process assumed a gas mixture of boron trichloride, ammonia, and argon (BCl3 + NH3 + 30Ar). The results indicated that boron trichloride governs the extent of penetration. The depths of penetration for the chemical vapor infiltration boron nitride (CVI-BN) process, conducted at 0.1 kPa within the temperature range of 1100–1400 K, were determined for pore diameters of 1, 10, 30, 100, 200 and 300 µm. When porosimetry data for a specific preform is available, the acquired penetration depth relationships for the CVI-BN process under specific parameters and process temperatures facilitate the estimation of essential parameters for interphase formation using pyrolytic boron nitride.

Aerosol derived carbon dots decorated boron nitride supported Zn-doped MoS2 for high performing flexible asymmetric supercapacitor

Alternative finding of toxic pollutant materials in proper utilization is a great challenge. Toxic and pollutant cigarette smoke having different π-conjugated organic components may work well as a precursor for carbon dots (CDs). In this work, cigarette smoke aerosol has been used for the synthesis of CDs and CDs have been further used for the fabrication of supercapacitor electrode. This methodology could be able to mitigate the two major problems-energy crisis and environment pollution. The smart combination of EDLC-type CDs deposited boron nitride (BN) and pseudocapacitive type Zn-doped MoS2 was able to enhance the supercapacitive performances. Heteroatom doping into MoS2 enhances the capacitive performances through the effective Faradic reactions. CDs and CDs deposited BN (CDs@BN) have been characterized using different characterization techniques. Zn-doped MoS2 has been uniformly grown on the CDs decorated BN (Zn–MoS2/CDs@BN) resulting in the stabilization of the electrode system. Zn–MoS2/CDs@BN nanohybrid delivered a specific capacitance (Sp.C) of 397 F/g in three-electrode system. Further, the asymmetric supercapacitor (ASC) device using Zn–MoS2/CDs@BN as cathode demonstrated wide potential range (up to 1.8 V) with a volumetric energy density of 3.42 mW h/cm3 and retaining a capacitance of ∼89% after 10,000 charging-discharging processes. Moreover, a flexible ASC device was made-up using viscous ionic electrolyte and it was able to glow a red LED, while it was bended in different angles. The methods described here will give a straightforward approach for using toxic-pollutant cigarette smoke to fabricate supercapacitor electrodes in order to compensate the upcoming energy crisis in a sustainable way.

Thermal and Electrical Properties of Additively Manufactured Polymer-Boron Nitride Composite.

The efficiency of electronic microchip-based devices increases with advancements in technology, while their size decreases. This miniaturization leads to significant overheating of various electronic components, such as power transistors, processors, and power diodes, leading to a reduction in their lifespan and reliability. To address this issue, researchers are exploring the use of materials that offer efficient heat dissipation. One promising material is a polymer-boron nitride composite. This paper focuses on 3D printing using digital light processing of a model of a composite radiator with different boron nitride fillings. The measured absolute values of the thermal conductivity of such a composite in the temperature range of 3-300 K strongly depend on the concentration of boron nitride. Filling the photopolymer with boron nitride leads to a change in the behavior of the volt-current curves, which may be associated with the occurrence of percolation currents during the deposition of boron nitride. The ab initio calculations show the behavior and spatial orientation of BN flakes under the influence of an external electric field at the atomic level. These results demonstrate the potential use of photopolymer-based composite materials filled with boron nitride, which are manufactured using additive techniques, in modern electronics.

On functional boron nitride: Electronic structures and thermal properties

• Summary of boron nitride polymorphs and structural stabilities. • Electronic and thermal transport in boron nitride, from bulk to lower dimensions. • Summary of state-of-the-art study on atomic-layer-deposition growth of boron nitride. • Current application of boron nitride and future perspectives. The past two decades have witnessed extensive explorations of boron nitride (BN) largely due to its unique optoelectronic properties, mechanical robustness, high thermal conductivity, thermal and chemical stability. Crystal growth and functional engineering of BN thin film structures as well as their integrations with two-dimensional materials for advanced applications have been attracting increasing interest in recent years. Here, we have reviewed the basic structural, electronic, and thermal transport properties of BN, especially hexagonal BN both in bulk and reduced dimensionalities. This is followed by a thorough account of progress in atomic layer deposition (ALD) of BN, which has the advantages of being able to grow on 3D surface and control the film thickness in atomic level. Future perspectives are provided through discussing the potential applications of BN along with the material synthesis.

Electrophoretic deposited boron nitride nanosheets-containing chitosan-based coating on Mg alloy for better corrosion resistance, biocompatibility and antibacterial properties

To reduce the degradation of magnesium alloy, improve its antibacterial activity, and fulfil specific requirements for bone implant material applications, a chitosan (CS)/boron nitride nanosheet (BNNS) composite coating was constructed on the surface of Mg–Zn–Y–Nd–Zr alloy via electrodeposition. The results show that BNNS was uniformly embedded and significantly changed the morphology and roughness of the CS coating. Electrochemical and immersion tests suggest that the CS–BNNS composite coating can effectively provide a long-term protection to the substrate. The antibacterial activity results show that BNNS significantly improved the antibacterial activity of the CS coating against E. coli and S. aureus, and verified the sterilisation mechanism of BNNS in contact with bacterial membranes. Meanwhile, cytocompatibility tests showed that the CS–BNNS coating has no adverse effect on the adhesion and proliferation of mouse osteoblasts cells. Thus, the fabricated CS–BNNS composite coating could be a promising application in surface modification for Mg-based bone implants.

Corrosion behavior of electrophoretically deposited boron nitride nanosheets on copper

The prime purpose of this research study is to determine the possibility of corrosion protection offered by boron nitride nanosheets (BNNSs) coated on pure Copper (Cu) strip through electrophoretic deposition (EPD). BNNSs suspension was developed by sonicating hexagonal boron nitride in isopropyl alcohol for 35 h prior to centrifugal partitioning of the supernatant solution, which contained BNNSs having thickness of ca. 11 nm as shown by atomic force microscopy. BNNSs deposition on copper substrate was processed in an EPD electrochemical cell arrangement keeping Cu metal as cathode and platinum as anode. The consequent BNNSs coating on the substrate was critically confirmed through series of microscopies adopting scanning electron, atomic force, and Fourier transform infrared. Energy dispersive x-ray analysis and x-ray diffraction techniques inferred the characterization positively. Tafel analysis and electrochemical impedance spectroscopy both were implied in order to evaluate  the corrosion behavior of coatings developed on substrate copper. The former confirmed an approximate sixfold enhancement in anti-corrosion capacity of copper protected by BN nanosheets than its bare form. The later, EIS analysis indicated a high impedance and charge transfer resistance ability of BNNSs coatings.

Atomic layer deposited boron nitride nanoscale films act as high temperature hydrogen barriers

Hydrogen environmental barrier coatings reduce hydrogen diffusion and concomitant hydrogen embrittlement of materials such as those used in nuclear and fuel cell applications where hydrogen is used as a fuel source. In this work, atomic layer deposition (ALD) was used to coat substrates with boron nitride (BN) films of approximately 6, 8, and 15 nm thicknesses. Differential thermal analysis of the coated samples in hydrogen gas showed resistance to reaction with hydrogen to at least 1713 K. Diffusion of atomic hydrogen into the hexagonal BN (001) surface and between sheets as well as material stability were computationally studied using density functional theory. A high activation energy of 3.25 eV was calculated for atomic hydrogen diffusion into the (001) hexagonal BN surface through a sheet. However, lower activation energies of 1.35 eV, 1.11 eV, and 0.12 eV were computed for unique hydrogen diffusion pathways between sheets, suggesting that sheet orientation parallel to the substrate surface is vital for attaining desirable barrier film properties. A predicted positive nitrogen vacancy formation energy of 4.3 eV at 2773 K suggests that hexagonal BN is stable at nuclear thermal propulsion operating temperatures, and stability was confirmed experimentally up to 1773 K.

Carbon Nano Tubes: Synthesis and Characterization for Microwave Applications

Attenuators are used to suppress the reflections in the helix traveling wave tubes and these attenuators are normally fabricated with the coating of some lossy material on the helix support rods. Carbon is the most commonly used attenuator material for the microwave applications and is usually deposited by pyrolytic or sputtering methods. However, other materials like iron and nickel are also used sometime for the attenuation applications. Helix is usually supported by the rods of some ceramic material like APBN (Anisotropic Pyrolytically Deposited Boron Nitride) or Alumina etc. Attenuator materials are deposited on these support rods to absorb the reflections. In order to look forward to new methods of deposition as well new attenuator materials, Carbon nanotubes have been proposed as another alternative attenuator material. Multi-Wall Cabon Nano-Tubes have been grown on the rectangular alumina substrate using the chemical vapour deposition method. Microwave attenuation/loss has been measured on these samples with X-band microwave frequencies. Specific experimental set-up has been designed for the measurement. The work is centered toward making good quality novel attenuators for the microwave applications and particularly the TWT.

Atomic Layer Deposition of Layered Boron Nitride for Large-Area 2D Electronics.

Hexagonal boron nitride (h-BN) has been considered a promising dielectric for two-dimensional (2D) material-based electronics due to its atomically smooth and charge-free interface with an in-plane lattice constant similar to that of graphene. Here, we report atomic layer deposition of boron nitride (ALD-BN) using BCl3 and NH3 precursors directly on thermal SiO2 substrates at a relatively low temperature of 600 °C. The films were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy wherein the uniform, atomically smooth, and nanocrystalline layered-BN thin film growth is observed. The growth rate is ∼0.042 nm/cycle at 600 °C, a temperature significantly lower than that of h-BN grown by chemical vapor deposition. The dielectric properties of the ALD-BN measured from Metal Oxide Semiconductor Capacitors are comparable with that of SiO2. Moreover, the ALD-BN exhibits a 2-fold increase in carrier mobility of graphene field effect transistors (G-FETs/ALD-BN/SiO2) due to the lower surface charge density and inert surface of ALD-BN in comparison to that of G-FETs fabricated on bare SiO2. Therefore, this work suggests that the transfer-free deposition of ALD-BN on SiO2 may be a promising candidate as a substrate for high performance graphene devices.

Influence of pressure on chemical vapor deposition of boron nitride from BCl3/NH3/H2 gas mixtures

Boron nitride (BN) was synthesized from BCl3/NH3/H2 precursor mixtures via chemical vapor deposition, with a focus on the influence of the total partial pressure of BCl3, NH3, and H2 (pBCl3+NH3+H2) on the surface deposition rate. The surface deposition rate of BN initially increased and then decreased with increasing pBCl3+NH3+H2, implying that the deposition process transitioned from surface reaction control to mass transfer control. BN deposition from BCl3 and NH3 was mainly attributable to several intermediate gaseous products containing B, N, Cl, and H, such as Cl2BNH2, ClB(NH2)2, and B(NH2)3. The microstructures of BN coatings deposited on SiC fibers were also analyzed. The BN coatings were uniformly and evenly deposited on the SiC fiber surfaces at low pBCl3+NH3+H2 values, whereas excessive pBCl3+NH3+H2 values afforded coatings containing large grains. The as-prepared BN coatings were stoichiometric but amorphous. Heat treatment substantially improved the texture and crystallinity to afford hexagonal BN.

Stabilizing Solid Electrolyte-Anode Interface in Li-Metal Batteries by Boron Nitride-Based Nanocomposite Coating

Summary Solid-state Li-metal batteries are promising to improve both safety and energy density compared to conventional Li-ion batteries. However, various high-performance and low-cost solid electrolytes are incompatible with Li, which is indispensable for enhancing energy density. Here, we utilize a chemically inert and mechanically robust boron nitride (BN) film as the interfacial protection to preclude the reduction of Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid electrolyte by Li, which is validated by in situ transmission electron microscopy. When combined with ∼1–2 μm PEO polymer electrolyte at the Li/BN interface, Li/Li symmetric cells show a cycle life of over 500 h at 0.3 mA·cm−2. In contrast, the same configuration with bare LATP dies after 81 h. The LiFePO4/LATP/BN/PEO/Li solid-state batteries show high capacity retention of 96.6% after 500 cycles. This study offers a general strategy to protect solid electrolytes that are unstable against Li and opens possibilities for adopting them in solid-state Li-metal batteries.

(Invited) A Comparative Study of Low-Temperature III-V Nitrides ALD in Thermal and Radical-Enhanced Modes

In the field of III-V nitrides, nowadays research is strongly focused on electron devices employing epitaxially grown gallium nitride (GaN) and aluminum gallium nitride (AlGaN) layers, as certain properties of these materials are superior to silicon. Still, the production of GaN/AlGaN in monocrystalline form leads to a high cost. Developing the polycrystalline films with cheaper production techniques may pave the way to more widespread adoption of these nitrides in microelectronics and lighting. Atomic layer deposition (ALD) allows in this light for less stringent (compared to epitaxial techniques) growth requirements, enabling reduced process temperatures and direct growth on a large variety of substrates, e.g., on Si and SiO2. ALD combines accurate thickness control with a high degree of uniformity and conformality. Despite of the growing number of publications w.r.t. various applications of the ALD poly-nitrides, the question if they exhibit competitive advantages for being implemented in electron devices remains open. It is generally accepted that due to a sufficient chemical activity of ammonia (NH3) with surface methyl groups (-CH3) after a trimethylaluminum (TMA) pulse, ALD of AlN readily occurs in purely thermal mode at low temperatures (< 370 oC). This is opposite to thermal deposition of GaN films from trimethylgallium (TMG) and NH3 precursors. It is reported that due to a low chemical activity of NH3 with the film surface after a TMG pulse, low-temperature deposition hardly occurs in purely thermal regime. The majority of reports on low-temperature deposition of GaN have therefore used additional means of activation (e.g., plasma) to dissociate NH3, thereby enhancing the reactivity with TMG-exposed surface by means of forming NHx radicals. This work reports on the deposition of GaN films at a temperature of 400 oC, in a purely thermal chemical mode using TMG and NH3, and compares that with plasma-enhanced GaN ALD. The demonstrated plasma-free process can be beneficial for industrial-scale batch-type reactors where uniform radical delivery is hard to achieve. The proposed approach utilizes the strong adduct-formation chemistry of the Lewis-acid TMG and the Lewis-base NH3 [1, 2] on the growth surface. Beyond a specific temperature, the TMG:NH3 surface adduct is expected to dissociate into Ga-NH2-Ga linkage, forming the first monolayer of GaN in a self-limiting fashion. Alternating pulses of TMG and NH3 with in-between purges therefore result in film growth from a sequence of such self-limiting surface reactions. The growth per cycle (GPC) has shown an increase with NH3 partial pressure [3], in accordance with the adduct reaction kinetics. This pressure-dependence of the growth has been in-situ monitored by spectroscopic ellipsometry (SE), revealing a maximum GPC value of 0.045 nm/cycle. The grazing incidence X-ray diffraction (GIXRD) scans confirmed polycrystalline wurtzitic structure of the GaN. The compositional depth profile obtained by X-ray photoelectron spectroscopy (XPS) revealed the formation of a stoichiometric GaN. The efficient removal of methyl groups (i.e., carbon) from the films has been confirmed by the low carbon content (1 at. %). Increasing the temperature from 400 oC to 550 oC activated the thermal decomposition of TMG, suppressing the adduct formation kinetics, breaking the mechanism of carbon removal from the films and thereby increasing the carbon content up to 10 at. %. The research efforts were further directed towards ALD of boron nitride (BN) films from BBr3 and NH3 precursors, exploring the role of adduct-formation chemistry in that process as well. The performed comparison between radical-enhanced and pure-thermal deposition of BN and GaN layers will be shown in the presentation, clarifying the film formation mechanisms. The purely thermal radical-free deposition of poly-GaN films will be highlighted, focussing on the growth mechanism, ALD window, and film properties. Ref.: [1] M. E. Bartram, T. A. Michalske, J. W. Rogers, Jr. and R. T. Paine, Chem. Mater. 5, 1424 (1993). [2] J. Randall Creighton and George T. Wang, J. Phys. Chem. A 109, 10554 (2005). [3] S. Banerjee, S. Dutta, A.A.I. Aarnink, J. Schmitz, D. J. Gravesteijn and A. Y. Kovalgin, “Purely thermal deposition of polycrystalline gallium nitride films at 400 oC”, submitted to ALD 2018 conference.

Controllable coating of boron nitride on ceramic fibers by CVD at low temperature

Boron nitride (BN) is a promising interface material for preparing continuous fiber reinforced ceramic matrix composites (CFCCs or CMCs). However, the controllable coating of BN on ceramic fibers remains a challenge. We developed a low-temperature chemical vapor deposition (CVD) approach for producing controllable coating BN on alumina fibers using ammonia borane (BH3NH3) as single source precursor at atmospheric pressure. The optimized sublimation temperature for BH3NH3 is 130°C and at this temperature the precursor could produce monomeric aminoborane (BH2NH2) and borazine (B3N3H6) for the subsequent CVD growth of BN. BN coatings obtained at the deposition temperature of 700°C was of high purity as confirmed by fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Scanning electron microscopy images of BN coated fibers indicated that the coatings produced under deposition temperature in the range of 700–900°C enwrapped on fibers continuously and tightly as the surface of the fiber was smooth and uniform. Annealing at a higher temperature of 1000 and 1300°C greatly improved the crystallinity of BN coatings deposited at 700°C as confirmed by grazing incidence X-ray diffraction and high resolution transmission electron microscopy characterization. Mechanism of this low-temperature CVD was investigated as well, and based on the understanding of deposition mechanism, the thickness and structure of the BN coatings could be controlled by turning the deposition temperature and duration. The tensile strength of alumina fibers before and after BN deposition at the temperature of 700, 800, and 900°C for 1.5h were investigated, and at the optimized deposition temperature of 700°C, the tensile strength retention was up to 94.9%, which demonstrates the great potential of this approach for fabricating high performance continues fiber reinforced ceramic matrix composites.

Mobility enhancement in graphene transistors on low temperature pulsed laser deposited boron nitride

Low temperature pulsed laser deposited (PLD) ultrathin boron nitride (BN) on SiO2 was investigated as a dielectric for graphene electronics, and a significant enhancement in electrical transport properties of graphene/PLD BN compared to graphene/SiO2 has been observed. Graphene synthesized by chemical vapor deposition and transferred on PLD deposited and annealed BN exhibited up to three times higher field effect mobility compared to graphene on the SiO2 substrate. Graphene field effect transistor devices fabricated on 5 nm BN/SiO2 (300 nm) yielded maximum hole and electron mobility of 4980 and 4200 cm2/V s, respectively. In addition, significant improvement in carrier homogeneity and reduction in extrinsic doping in graphene on BN has been observed. An average Dirac point of 3.5 V and residual carrier concentration of 7.65 × 1011 cm−2 was observed for graphene transferred on 5 nm BN at ambient condition. The overall performance improvement on PLD BN can be attributed to dielectric screening of charged impurities, similar crystal structure and phonon modes, and reduced substrate induced doping.

Thermodynamic study on the chemical vapor deposition of boron nitride from the BCl3–NH3–H2 system

The gas-phase reaction thermodynamics in the chemical vapor deposition (CVD) process of preparing boron nitride with the precursors of BCl3–NH3–H2 was investigated with a relatively complete set of 144 species, in which the thermochemistry data were calculated with accurate model chemistry at G3(MP2) and G3//B3LYP levels combined with standard statistical thermodynamics. The data include the heat capacities, entropies, enthalpies of formation, and Gibbs free energies of formation. Three different modifications of condensed phase boron nitride (hexagonal h-BN, cubic c-BN, and wurtzite w-BN) were taken into consideration. Based on these data, the distribution of the equilibrium concentration of the 144 species was obtained with the principle of chemical equilibrium. It was concluded that c-BN is formed at temperatures up to 1,800 K, h-BN is the most stable above this temperature, and w-BN is unstable under considerable conditions.

Fabrication of AlN/BN bishell hollow nanofibers by electrospinning and atomic layer deposition

Aluminum nitride (AlN)/boron nitride (BN) bishell hollow nanofibers (HNFs) have been fabricated by successive atomic layer deposition (ALD) of AlN and sequential chemical vapor deposition (CVD) of BN on electrospun polymeric nanofibrous template. A four-step fabrication process was utilized: (i) fabrication of polymeric (nylon 6,6) nanofibers via electrospinning, (ii) hollow cathode plasma-assisted ALD of AlN at 100 °C onto electrospun polymeric nanofibers, (iii) calcination at 500 °C for 2 h in order to remove the polymeric template, and (iv) sequential CVD growth of BN at 450 °C. AlN/BN HNFs have been characterized for their chemical composition, surface morphology, crystal structure, and internal nanostructure using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Measurements confirmed the presence of crystalline hexagonal BN and AlN within the three dimensional (3D) network of bishell HNFs with relatively low impurity content. In contrast to the smooth surface of the inner AlN layer, outer BN coating showed a highly rough 3D morphology in the form of BN nano-needle crystallites. It is shown that the combination of electrospinning and plasma-assisted low-temperature ALD/CVD can produce highly controlled multi-layered bishell nitride ceramic hollow nanostructures. While electrospinning enables easy fabrication of nanofibrous template, self-limiting reactions of plasma-assisted ALD and sequential CVD provide control over the wall thicknesses of AlN and BN layers with sub-nanometer accuracy.

Effects of nitrogen gas ratio on magnetron sputtering deposited boron nitride films

Transformation from h-BN (boron nitride) to fullerene-like e-BN with increasing N2 ratios (fN2, 20–33%) has been found in a radio frequency magnetron sputtering deposition by using Fourier transform infrared spectroscopy (FTIR). X-ray photoelectron spectroscopy (XPS) examination suggests that the stoichiometric e-BN molecule contains equal numbers of sp3 and sp2 bonds at fN2=33%. The surface morphology and corresponding roughness of as-deposited BN films were evaluated by Atomic force microscopy (AFM).

Investigation of Boron Nitride Prepared by Low Pressure Chemical Vapor Deposition at 650~1200 °C

Boron nitride (BN) coatings were deposited on carbon substrates by low pressure chemical vapor deposition (LPCVD) in a large temperature range of 650~1200 °C, employing BCl3-NH3-H2 reaction system. The effects of depositing temperature on the yield, control step of deposition progress (deposition mechanism), microstructure, and crystallization degree of BN coating were investigated. Results show that BN deposition rate first increases and then decreases as the rising temperature and the maximum deposition rate occurs at 900~1000 °C. By the determination of the Arrenius relationship, there are three temperature regions with different active energies and controlled by different deposition mechanisms, i.e. chemical reaction, mass transport and depletion of reactants. Through the surface morphology observation by scanning electron microscopy (SEM), chemical composition analyses by energy dispersion spectroscopy (EDS) and crystallization degree and grain size comparison by Raman spectroscopy, it can be drawn that interphase-used BN is suitable to be deposited at 1000 °C.

On the effect of water and oxygen in chemical vapor deposition of boron nitride

Growth studies of sp2-hybridized boron nitride (BN) phases by thermal chemical vapor deposition (CVD) are presented; of particular interest is the presence of oxygen and water during growth. While Fourier transform infrared spectroscopy reveals the presence of BN bonds and elemental analysis by elastic recoil detection analysis shows that the films are close to stoichiometric, although containing a few atomic percent oxygen and hydrogen, X-ray diffraction measurements show no indications for nucleation of any crystalline BN phases, despite change in N/B-ratio and/or process temperature. Thermodynamic modeling suggests that this is due to formation of strong BO bonds already in the gas phase in the presence of water or oxygen during growth. This growth behavior is believed to be caused by an uncontrolled release of water and/or oxygen in the deposition chamber and highlights the sensitivity of the BN CVD process towards oxygen and water.