BN Target Research Articles

Electrical Characterization of Hydrogenated Boron Carbon Nitride Thin Films at Cryogenic Temperatures

Compounds in boron-carbon-nitrogen ternary triangle such as diamond (C), cubic boron nitride (c-BN), and boron carbide (B4C) have gained attention due to their covalent bonding, short bond lengths, low atomic mass[1]. These materials exhibit low dielectric values along with excellent mechanical and thermal strength. Boron carbon nitride (BCN) compounds are known to combine unique properties of boron carbide and boron nitride, with the properties being tunable with varying elemental composition and structure. These outstanding properties have made BCN attractive and finds multi-functional applications in anti-wear and protective coatings, supercapacitors, UV detectors, nanobiotechnology and nanomedicine[2]. BCN thin films also find opto-electronic applications in the harsh environments. While addition of small amounts of hydrogen has been proven beneficial for electrical and optical properties in BCN films, the electrical behavior of hydrogenated BCN films at low temperatures is not evaluated. Such evaluations will further expand the use of of hydrogenated BCN for extreme temperature applications.In this study, BCN thin films are deposited using RF magnetron sputtering with varying hydrogen/nitrogen gas flows. Substrate temperature is kept constant at room temperature. Dual target sputtering from B4C and BN targets is performed to deposit BCN thin films. I-V characterization is performed from room temperature to 70 K. The variation in resistivity with reactive gas flow rate at low temperature is reported.

Nanoindentation and Photoluminescence Studies on Hydrogenated Boron Carbon Nitride Thin Films

Compounds in boron-carbon-nitrogen ternary triangle such as diamond (C), cubic boron nitride (c-BN), and boron carbide (B4C) have gained attention due to their covalent bonding, short bond lengths, low atomic mass[1]. These materials exhibit low dielectric values along with excellent mechanical and thermal strength. Boron carbon nitride (BCN) compounds are known to combine unique properties of boron carbide and boron nitride, with the properties being tunable with varying elemental composition and structure. These outstanding properties have made BCN attractive and finds multi-functional applications in anti-wear and protective coatings, supercapacitors, UV detectors, nanobiotechnology and nanomedicine[2]. While addition of small amounts of hydrogen has been proven beneficial for electrical and optical properties in BCN films, the influence of hydrogen on mechanical properties have not yet been reported.In this study, BCN thin films are deposited using RF magnetron sputtering with varying hydrogen/nitrogen gas flows and substrate deposition temperature. Dual target sputtering from B4C and BN targets is performed to deposit BCN thin films. The chemical composition, hardness, Young’s modulus and photoluminescence properties of BCN films are measured as a function of gas flow and substrate temperatures. Hardness of the BCN films range between 6 – 22 GPa and Young’s modulus between 125 – 140 GPa. Photoluminescence (PL) studies are performed at room temperature and 77K. PL peak shifts are observed in BCN films deposited at different substrate temperatures.

Nanoindentation and Photoluminescence Studies of Hydrogenated Boron Carbon Nitride Thin Films

Nanoindentation and photoluminescence (PL) studies were performed on hydrogenated boron carbon nitride thin films deposited using radio frequency magnetron sputtering. Dual target sputtering from B4C and BN targets was used to deposit films. The variation in the composition of films was studied using energy-dispersive X-ray spectroscopy. The influence of hydrogen gas and substrate temperature on the mechanical properties was investigated using nanoindentation measurements. Photoluminescence studies were performed on films deposited under varying hydrogen content and different deposition temperatures. The films deposited in this study exhibited hardness of 6–22 GPa and Young’s modulus of 125–140 GPa. PL spectra demonstrated two prominent emission peaks around 499 nm and 602 nm for the deposited films. Increasing the hydrogen gas ratio in the films induced PL peak shifts to longer wavelengths. Emission spectra shifted to long wavelength with increasing substrate temperature. The emission peak position shifted from 499 nm to 544 nm and from 602 nm to 655 nm as a function of substrate temperature. For the first time, BCNH based thin films PL behavior at low temperature (77 K) has been characterized in this study. The BCNH thin films show a rare phenomenon of negative thermal quenching of emission.

The structure and optical properties of C doped BN thin films deposited by RF reactive magnetron sputtering

The C doped BN thin films were assembled on Si (1 1 1) and quartz substrates utilizing BN target by magnetron sputtering with CH4 as reactive gas and Ar as working gas. Atomic force microscopy (AFM), Raman, X-ray photoelectron spectroscopy (XPS) and UV–visible (UV–vis) spectrophotometer are conducted to test and analyze the structures and optical properties of the thin films. The films deposited at various CH4 flow possess compact and uniform surface. All thin films are mainly composed of B–N, B–C and C–N chemical bonds. Raman spectra show that ID/IG in the thin films increases with the growing of gas flow rate ratio (R = FCH4/(FCH4+FAr)). Moreover, the optical band gap (Eg) of the C doped BN thin films is ranging from 4.04 to 5.16 eV. In addition, the Eg value of the C doped BN thin films decreased with the growing of R. This was owing to the increase of carbon content since this contributed to the increase of π bonding originating from CC bond.

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.

Investigation on Electrical Properties of Hydrogen Doped Sputtered Boron Carbon Nitride Thin Films

Interlayer dielectric materials (ILD) play a crucial role of isolating electrically conductive and semiconducting features on the devices [1]. Due to constant scaling down of device dimensions, the interconnect delay (τ = R x C) can be reduced by decreasing resistance of conductor and capacitance of ILD. Reduced capacitance can be achieved by high quality insulating film with low dielectric constant. Boron carbon nitride (BCN) films have achieved attention due to their complicated crystalline structure and unique properties. Atomic bonding similarities amongst boron, carbon and nitrogen allow formation of compounds with wide compositional range. BCN compounds are expected to combine the excellent properties of diamond, B4C and BN with their properties adaptable depending on their composition and structure [2, 3]. In this study, electrical properties of hydrogen doped BCN thin films will be investigated. BCN films are sputtered by B4C and BN targets. Films are deposited at different temperatures in presence of hydrogen/argon to investigate the influence of temperature and hydrogen gas on the electrical properties of BCN thin films.

A brief overview of RF sputtering deposition of boron carbon nitride (BCN) thin films

A great part of interest has been paid for fabricating new materials with novel mechanical, optical, and electrical properties. Boron carbon nitride (BCN) ternary system was applied for variable bandgap semiconductors and systems with extreme hardness. The purpose of this literature review is to provide a brief historical overview of B4C and BN, to review recent research trends in the BCN synthesizes, and to summarize the fabrication of BCN thin films by plasma sputtering technique from B4C and BN targets in different gas atmospheres. Pre-set criteria are used to discuss the processing parameters affecting BCN performance which includes the gasses flow ratio and effect of temperature. Moreover, many characterization studies such as mechanical, etching, optical, photoluminescence, XPS, and corrosion studies of the RF sputtered BCN thin films are also covered. We further mentioned the application of BCN thin films to enhance the electrical properties of metal-insulator-metal (MIM) devices according to a previous report of Prakash et al. (Opt. Lett. 41, 4249, 2016).

BN coatings deposition by magnetron sputtering of B and BN targets in electron beam generated plasma

Boron nitride coatings were deposited by reactive pulsed magnetron sputtering of B and BN targets (50 kHz, 10 µs for B; 13.56 MHz for BN) at 2–20 mA/cm2 ion current density on the substrate. The effect of electron beam generated plasma on characteristics of magnetron discharge and phase composition of coatings was studied.

Proton induced gamma-ray production cross sections and thick-target yields for boron, nitrogen and silicon

The excitation functions for the reactions 14N(p,p′γ)14N, 28Si(p,p′γ)28Si and 29Si(p,p′γ)29Si were measured at an angle of 55° by bombarding a thin Si3N4 target with protons in the energy range of 3.6–6.9MeV. The deduced γ-ray production cross section data is compared with available literature data relevant for ion beam analytical work. Thick-target γ-ray yields for boron, nitrogen and silicon were measured at 4.0, 4.5, 5.0, 5.5, 6.0 and 6.5MeV proton energies utilizing thick BN and Si3N4 targets. The measured yield values are put together with available yield data found in the literature. The experimental yield data has been used to cross-check the γ-ray production cross section values by comparing them with calculated thick-target yields deduced from the present and literature experimental excitation curves. All values were found to be in reasonable agreement taking into account the experimental uncertainties.

Deposition and XPS studies of dual sputtered BCN thin films

Thin films of boron carbon nitride (BCN) are deposited by co-sputtering of B4C (Direct Current—DC) and BN (Radio frequency—RF) targets with varying N2/Ar gas flow ratio and DC target power. BCN being a low-k material and a potential inter layer dielectric (ILD), the deposition and surface analysis become prime factors for ultra large scale integration (ULSI) process and device integration. In this study, a thorough analysis on deposition rate of BCN thin films is conducted as a function of various N2/Ar gas flow ratios, target powers and substrate deposition temperatures. XPS studies are conducted to ascertain the chemical composition and bonding of the deposited BCN films for the various deposition parameters. The deposition rate is found to show a decreasing trend with an increase in substrate deposition temperature but showed an increasing trend at 400°C. As the sputtering yield of B4C target is far greater than that of BN target, the deposition rate and XPS studies are conducted for the target powers of 20W and 40W for the B4C target. The deposition rate showed a decreasing trend from N2/Ar=0.25 to 0.75, but increases at N2/Ar=1. The XPS characterization indicates the formation of BCN phase distinctly with few separate phases of CN and BN.

Feasibility of Etching Studies on BCN Thin Films

Investigation of wet chemical etching Boron carbon nitride (BCN) thin films deposited by dual magnetron sputtering of B4C (DC) and BN (RF) targets was conducted. BCN, a low-k dielectric material, is a potential candidate as inter-layer dielectric (ILD) in VLSI process. A common aluminum etchant consisting of phosphoric acid (H3PO4), nitric acid (HNO3) and acetic acid (CH3COOH) was tested for its feasibility as a good etchant for BCN thin films. The etching studies were performed on BCN films that were deposited at room temperature, 200°C and 300°C as a function of various N2/Ar gas flow ratios in an rf sputtering technique. It was found that the film deposited at higher temperatures shows lower etching rate trends. Activation energies (Ea) were calculated for each N2/Ar gas flow ratio with the help of Arrhenius plots and compared with respect to elemental compositions of the films.

Optical Studies of Reactively Co-Sputtered BCN Thin Films

Boron carbon nitride (BCN) ternary compounds have similarities in the structure and difference in properties between graphite and hexagonal boron nitride (h-BN). Both theoretical calculations and experimental studies show that BCN compounds exhibit excellent mechanical, optical and electrical properties. The possibility to control the band gap (EG) by atomic composition and structure makes them good candidates for the application in electronic and photonic devices . In this work we deposited BCN thin films on quartz substrates by B4C and BN targets using RF and DC powers respectively at different N2/Ar gas flow ratios. Input power for B4C and BN are varied to achieve different composition of the BCN thin films to control the optical properties. The optical properties like transmission and reflectance are studied using the UV-visible spectrophotometer. The optical absorption is studied by Tauc plot which is instrumental in finding the optical band gap of the material and the refractive index.

Effect of deposition temperature on the alignment of hexagonal laminates in turbostratic boron nitride thin film

The deposition behavior of turbostratic boron nitride (t-BN) films was investigated with the focus on its microstructure variation in relation to deposition temperature substrate bias voltage. BN films were deposited using the unbalanced magnetron sputtering method. Thin (100μm) Si strips (3×40mm2) coated with a nanocrystalline diamond thin layer were used as substrates. A BN target was used, which was connected to a radio frequency power supply set at 400W. A pulsed direct current power supply connected to a substrate holder was used for negative biasing. The deposition pressure was 0.27Pa with a flow of Ar (18sccm)–N2 (2sccm) mixed gas. Only t-BN films were deposited with the substrate bias less than −100V irrespective of the deposition temperature. The orientation of (0002) t-BN laminate alignment changed from normal to parallel to the substrate surface with increased deposition temperature. High resolution transmission electron microscopy and Fourier transform infrared spectroscopy confirmed such behavior. However, the application of bias voltage made the (0002) laminates align normal to the substrate surface even at high deposition temperatures. The films tended to react with moisture in an ambient atmosphere as confirmed by the appearance of OH absorption peak in the FTIR spectrum. The measured OH absorption intensity was not influenced by the variation of deposition variables.

Mechanical, tribological and corrosion properties of CrBN films deposited by combined direct current and radio frequency magnetron sputtering

Cr–B–N films were deposited on stainless steel substrates by a combined direct current and radio frequency (RF) reactive unbalanced magnetron sputtering process using two elemental Cr and one compound BN targets. Boron content in the as-deposited films was qualitatively analyzed by time-of-flight secondary ion mass spectroscopy. Films' microstructure, mechanical and tribological properties were characterized by X-ray diffraction, nanoindentation and pin-on-disk tribometer experiments. Corrosion behavior of the Cr–B–N films was evaluated by electrochemical potentiodynamic polarization method in a 3wt.% NaCl solution. All the films were crystallized into a NaCl-type cubic structure. At lower RF power applied on the BN target (≤600W), films are relatively randomly oriented, and films' crystallinity increased with increasing RF power. With increasing RF power further (≥800W), films became (200) preferentially oriented, and films' crystallinity decreased gradually. With incorporation of a small amount of boron atoms into the CrN films, hardness, wear- and corrosion-resistance were all improved evidently. The best wear and corrosion resistance was obtained for the film deposited with 600W RF power applied on the BN target.

Hexagonal boron nitride nanowalls: physical vapour deposition, 2D/3D morphology and spectroscopic analysis

Hexagonal boron nitride nanowalls were synthesized using reactive radio-frequency magnetron sputtering in combination with a hexagonal BN target. The nanowall formation is purely governed by addition of hydrogen to the nitrogen/argon gas mixture, and leads to a decreased incorporation of carbon and oxygen impurities. The surface morphology is assessed with scanning electron microscopy, while stoichiometry and reduced impurity content of the material was evidenced using Rutherford backscattering spectroscopy. Transmission electron microscopy confirms the hexagonal nature of the nanowalls, whose luminescent properties are studied with cathodoluminescence spectroscopy, shedding more light on the location and nature of the excitonic emission and crystalline quality of the h-BN nanowalls.

Excitation wavelength dependence of water-window line emissions from boron-nitride laser-produced plasmas

We investigated the effects of laser excitation wavelength on water-window emission lines of laser-produced boron-nitride plasmas. Plasmas are produced by focusing 1064 nm and harmonically generated 532 and 266 nm radiation from a Nd:YAG laser on BN target in vacuum. Soft x-ray emission lines in the water-window region are recorded using a grazing-incidence spectrograph. Filtered photodiodes are used to obtain complementary data for water-window emission intensity and angular dependence. Spectral emission intensity changes in nitrogen Ly-α and He-α are used to show how laser wavelength affects emission. Our results show that the relative intensity of spectral lines is laser wavelength dependent, with the ratio of Ly-α to He-α emission intensity decreasing as laser wavelength is shortened. Filtered photodiode measurements of angular dependence showed that 266 and 532 nm laser wavelengths produce uniform emission.

Deposition and Adhesion Characterization of Ti(BN:MoS2) Based Composite Thin Films Prepared by Closed-Field Unbalanced Magnetron Sputtering

Composite structured solid thin films were deposited on 52100 tool steel by co-sputtering from BN, TiB2, MoS2 and Ti targets using a closed-field unbalanced magnetron sputtering process (CFUBMS). The structural and mechanical properties of the composite structured coatings were investigated. The composition and morphology of the films were investigated using X-ray diffraction and scanning electron microscopy (SEM). The adhesion properties of the films were characterized by the use of a Revetest-scratch tester. The adhesion test results indicated that bias voltage was the most effective coating parameter related to the critical load.

Microstructure and Mechanical Properties of Cr-Al-B-N Coatings Prepared by Reactive D.C. and R.F. Co-Sputtering

The current study was undertaken to investigate the synthesis of CrAlN/BN composite coatings having super high hardness by a reactive co-sputtering using CrAl alloy and BN targets and gaseous mixture of Ar+N2, in order to eliminate the possible formation of boride bonding. CrAlN or BN phase was deposited by pulsed d.c.- and r.f.- sputtering, respectively. Plastic hardness, Hpl, and Young’s modulus, E*, of the coatings increased with BN phase ratio, reaching a maximum value of ~46 GPa and 390 GPa at ~8 vol. % of BN phase; and then decreased to ~20GPa and ~300GPa at ~18 vol.%, respectively. Only B1 structured Cr(Al)N phase was found in XRD and SAED analysis. XPS and TEM/HRTEM results revealed that the CrAlN/8vol%BN coating consists mostly of CrAlN and BN phase, which exists as an amorphous like phase among the CrAlN grains. The CrAlN/8vol%BN coating has a kind of nanocomposite structure and the super high hardness over 40 GPa is probably due to this structure.

Structure, hardness and thermal stability of TiAlBN coatings grown by alternating deposition of TiAlN and BN

Hardness and thermal stability of TiAlBN coatings prepared by alternating deposition of TiAlN and BN with high rotation speed of substrate holder (∼7 rpm) have been investigated. The TiAlN and BN were deposited by reactive sputtering of Ti 0.5Al 0.5 and BN targets with N 2 and Ar reactive gases, respectively. Despite alternating deposition, the TiAlBN coating did not show layered structure due to high rotation speed of substrate holder. By TEM analysis, the TiAlBN coating was observed to be nanocomposite with grain less than 10 nm in size. Compared to TiAlN coating, the TiAlBN nanocomposite coating showed superior hardness. Furthermore, the hardness of the coating increased after the heat-treatment in N 2 atmosphere up to 800 °C. By comparison with TiAlN/BN nanoscale multilayered coating prepared by the same deposition method except the lower rotation speed of substrate holder (∼1 rpm), the hardness enhancement after annealing, ‘self-hardening’, of the TiAlBN nanocomposite coating is believed to be due to the sharpness in chemical composition at the interface between TiAlN and BN phase.

Magnetron sputter deposition of low-stress, carbon-containing cubic boron nitride films using Ar―N2―CH4 gas mixtures

Cubic boron nitride (c-BN) films produced by PVD and plasma-assisted CVD techniques typically exhibit undesired high compressive stresses. One of the effective and feasible methods to reduce stress and hence improve film adhesion has been a controlled addition of a third element into the film during deposition. In the present study, BN films were grown on to silicon substrates using reactive magnetron sputtering with a hexagonal BN target. An auxiliary flow of methane was mixed into argon and nitrogen as the working gas. The deposition was conducted at various methane flow rates at 400°C substrate temperature, 0.2Pa total working pressure, and −250V r.f. substrate bias. The microstructure of the deposited films was then examined in dependence of the methane flow rate. With increasing methane flow rate from 0 to approx. 2.0sccm, the fraction of the cubic BN phase in the deposited films decreased gradually down to approx. 75vol.%, whereas the film stress was reduced much more rapidly and almost linearly in relation to the methane flow rate. At 2.1sccm methane, the stress became approx. 3 times reduced. Owing to the significantly decreased film stress, adherent, micrometer thick, cubic-phase dominant films can be allowed to form on silicon substrate. The microstructure of the films will be illustrated through FTIR and XRR.