RF Induction Research Articles

Eutectic Bonding Utilizing Radio Frequency Induction Heating for Fabricating Vertical Light-Emitting Diodes

Vertical light-emitting diodes (VLEDs) have attracted considerable attention owing to their improved thermal, electrical, and optical performance compared to conventional LEDs. To fabricate VLEDs, a bonding technique is required following laser lift-off. Eutectic bonding techniques are preferred owing to their low-heat mechanism and production safety. However, the conventional resistance heating method for eutectic bonding process, the extremely longer process time becomes a problem such as cost rise, wapage. In this study, the thermal efficiency was measured according to the diameter of the coil in order to optimize the eutectic bonding of the RF induction heating method in order to solve this problem. We confirmed that successful eutectic bonding is possible with less than 30 min processing using Sn-Glass. In addition, Au (20 wt%)/Sn (80 wt%) alloy, a mainly used the eutectic bonding interlayer material for VLEDs, can also be used as an interlayer to provide void-free eutectic bonding in less than 30 min.

Plasma parameters in a dual-camera low-power inductive RF discharge with an external magnetic field

The results from studying a dual-camera inductive radio-frequency (RF) discharge that was placed in an external magnetic field are presented. The operating conditions were as follows: an argon pressure of 5 × 10–5–6 × 10–2 Torr, an external magnetic field strength of 0–60 G, and an RF generator power supply of 25–300 W. During the experiment the resonant RF power consumption and the correspondence between the local power-consumption maxima and spatial maxima of the plasma concentration as a function of the external magnetic field were observed. The comparison of the experimental results with the results of the mathematical simulation indicates that the resonant character of the discharge is associated with the excitation of helicons and Trivelpiece–Gould waves.

Rapidly Quenched Ni45Fe5Mn40Sn10 Heusler Alloys

The present work describes the synthesis and characterization of Ni45Fe5Mn40Sn10 Heusler alloys. The constituent pure metals were melted in radio frequency induction furnace to form the alloy and then cooled it quickly. The as-cast alloy was annealed at 850 °C for 24 h in vacuum and cooled in two different conditions i.e. self-cooling at room temperature in air and sudden cooling at liquid nitrogen temperature (quenched). The X-ray diffraction, scanning and transmission electron microscopic techniques have been used for structural/microstructural characterization as well as chemical analysis of the material. The effect of annealing and subsequent cooling in two different conditions has been described and discussed in the context of evolution of B2 and orthorhombic martensite with lattice parameter a= 0.65 nm, b=0.59 nm and c=0.56 nm.

Morphology simulation of the surface subjected to low-energy ion sputtering

A new 2D method of simulating the morphology of a surface subjected to low-energy ion sputtering with regard to sputtered material redeposition is suggested. The object of simulation is the profile of microgrooves arising on the silicon surface exposed to slow argon ions from the dense plasma of an rf induction discharge. Numerical simulation data and experimental data are in good agreement.

저항가열 방식을 적용한 승화법에 의한 SiC 결정 성장에 대한 연구

SiC 결정은 전력반도체 소자용 소재로서 지금까지 외국은 물론 국내에서도 많은 연구가 이루어지고 있으며, 지금까지 고주파 유도가열 방식을 이용한 승화법으로 성장되어 왔다. 그러나, SiC 단결정은 결정 성장 계면에서의 온도 안정성에 따라 쉽게 다른 다형으로 성장하기 때문에, 고품질의 결정을 얻기 위해서는 결정성장 계면에서의 안정적인 온도 구배가 필요하다. 본 논문에서는 저항가열 방식을 이용한 승화법 성장 장치를 이용하여 종자결정을 사용하지 않은 상태에서 SIC 다결정상을 성장하여 보고, 성장 양상에 대하여 고찰하고자 하였다. SiC 다결정상은 성장속도 0.02~0.5 mm/hr로 성장되었으며, 성장된 SiC 다결정상의 두께는 0.25 mm~0.5 mm이고, 이 때 도가니 하부의 온도는 <TEX>$2100{\sim}2300^{\circ}C$</TEX>, 성장 압력은 10~760 torr의 범위에서 조절되었다. 성장된 다결정상 결정은 광학현미경으로 관찰하여, 성장 거동을 고찰하였다. SiC crystals are well known for their true potential as high power devices and their crystal growth activity is actively carried out in domestic as well as in abroad. Until now the process to grow this crystal has been done by sublimation technique using radio frequency induction heating method. However in order to get better quality of SiC crystals, the stability of temperature is needed because SiC crystal tends to transform to other polytypes. So, the possibility of SiC crytals growth was evaluated by different heating method. This study aimed to observe whether the resistant heating method would show stable growth and better quality of SiC single crystal than that of RF induction heating. As a result, polycrystalline SiC crystals were grown by the growth rate of 0.02~0.5 mm/hr under the condition of <TEX>$2100{\sim}2300^{\circ}C$</TEX> at the bottom side of the crucible and 10~760 torr. The polycrystalline SiC crystals with 0.25 and 0.5 mm in thickness were grown successfully without seed and characterized by optical stereo microscopic observation.

Physicochemically functionalized carbon nanohorns for multi-dimensional cancer elimination

We have developed multi-componential nanomaterials that are based on folic acid (FA) and polyethylenimine-functionalized carbon nanohorn conjugates that encapsulate magnetite nanoparticles. The nanoconjugates were characterized using a variety of experimental setups, including dynamic light scattering, thermogravimetric analysis, Fourier transform infrared spectrometry, and ultraviolet–visible–near-infrared (UV–Vis–NIR) spectroscopy. An NIR laser and a radio frequency-induction heating system were used to evaluate the heat-generating capability of the nanoconjugates. Aqueous solutions containing the nanoconjugates exhibited a significant increase in temperature after laser irradiation and/or radio frequency induction compared with controls. The intercellular distribution of the nanoconjugates was quantitatively analyzed using UV–Vis–NIR spectroscopy with two cell lines: human epidermal carcinoma (KB) and human embryonic (FHs173We) cells. The interaction between the FA-modified nanoconjugates and KB cells was enhanced through overexpression of FA receptors on the surface of the KB cells. A stronger interaction between the nanoconjugates and KB cells was observed in the presence of a magnet. Furthermore, laser- and/or radio frequency-induced nanoconjugates in combination with external magnetic application reduced the viability of KB cells. Therefore, the present study will open a new direction for the development of multi-dimensional cancer therapy.

Synthesis of carbon nanostructures in an RF induction plasmatron

The method and results of synthesizing carbon nanotubes and onion-like structures by the sublimation of a mixture of a carbon powder with a catalyst (Y2(CO3)3) in the plasma flow of an inert gas (argon) generated in an rf plasmatron are described. Carbon vapors are condensed into fullerene-containing soot onto various materials (Al, Cu, Ti, stainless steel) placed in the working chamber of an experimental setup. The composition of the synthesized soot is analyzed by modern highly informative methods (Raman spectroscopy, transmission electron microscopy, X-ray diffraction). Single-wall carbon nanotubes of a small diameter (1.2 nm) and onion-like structures 10–20 nm in size are formed in experiments. In a reference experiment on a mixture of argon and methane, a material, which consists of a mixture of amorphous carbon, nanosized graphite, and graphite with a crystallite size of several microns, is synthesized. The effect of the substrate material, the gas pressure, and the plasma flow velocity on the formation of carbon nanotubes is studied.

Thermal stability of β-Ga2O3 in mixed flows of H2 and N2

The thermal stability of β-Ga2O3(010) substrates was investigated at atmospheric pressure between 250 and 1450 °C in a flow of either N2 or a mixture of H2 and N2 using a radio-frequency induction furnace. The β-Ga2O3 surface was found to decompose at and above 1150 °C in N2, while the decomposition of β-Ga2O3 began at only 350 °C in the presence of H2. Heating β-Ga2O3 substrates in gas flows containing different molar fractions of H2 demonstrated that the decomposition was promoted by increasing the H2 molar fractions. Thermodynamic analysis showed that the dominant reactions are in N2 and in a mixed flow of H2 and N2. The second-order reaction with respect to H2 determined for the mixed flows agrees with the experimental results for the dependence of the β-Ga2O3 decomposition rates on the H2 molar fraction.

Synthesis of uniform α-Si3N4 nanospheres by RF induction thermal plasma and their application in high thermal conductive nanocomposites.

In this paper, single-crystalline α-Si3N4 nanospheres with uniform size of ∼50 nm are successfully synthesized by using a radio frequency (RF) thermal plasma system in a one-step and continuous way. All Si3N4 nanoparticles present nearly perfect spherical shape with a narrow size distribution, and the diameter is well-controlled by changing the feeding rate. Compact Si3N4/PR (PR = phenolic resin) composites with high thermal conductivity, excellent temperature stability, low dielectric loss tangent, and enhanced breakdown strength are obtained by incorporating the as-synthesized Si3N4 nanospheres. These enhanced properties are the results of good compatibility and strong interfacial adhesion between compact Si3N4 nanospheres and polymer matrix, as large amount of Si3N4 nanospheres can uniformly disperse in the polymer matrix and form thermal conductive networks for diffusion of heat flow.

Preparation of few-layer graphene nanosheets by radio-frequency induction thermal plasma

Graphene nanosheets (GNs) are successfully deposited via a radio frequency (RF) induction thermal plasma pyrolysis process using methane as the precursor. Products are characterized by X-ray powder diffractometer (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy and BET measurements. The results illustrate that those few-layer GNs with the number of layer at about 5 and the size at 200–500nm are deposited. The H2 atmosphere in the RF induction thermal plasma is the key factor to fabricate the few-layer GNs. The direct conversion of CH4 to few-layer GNs through RF thermal plasma process suggests that the technique is simple, easy to operate, and is suitable for mass production of few-layer GNs in a continuous and scalable process.

Resolving an anomaly in electron temperature measurement using double and triple Langmuir probes

Langmuir probes with variants such as single, double and triple probes remain the most common method of electron temperature measurement in low-temperature laboratory plasmas. However, proper estimation of electron temperature mainly using triple probe configuration requires the proper choice of compensation factor (W). Determination of the compensating factor is not very straightforward as it depends heavily on plasma floating potential (Vf), electron temperature (Te), the type of gas used for plasma production and the bias voltage applied to probe pins, especially in cases where there are substantial variations in floating potential. In this paper we highlight the anomaly in electron temperature measurement using double and triple Langmuir probe techniques as well as the proper determination of the compensation factor (W) to overcome this anomaly. Experiments are carried out with helicon antenna producing inductive radiofrequency plasmas, where significant variation of floating potential along the axis enables a detailed study of deviations introduced in Te measurements using triple probes compared to double and single probes. It is observed that the bias voltage between the probe pins of the triple probes plays an important role in the accurate determination of the compensating factor (W) and should be in the range (5Vd2 < Vd3 < 10Vd2), where Vd2 and Vd3 are the voltage between floating probe pins 2 and 1 and the bias voltage, respectively.

Development of a new deuterium–deuterium (D–D) neutron generator for prompt gamma-ray neutron activation analysis

A new deuterium–deuterium (D–D) neutron generator has been developed by Adelphi Technology for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA), and fast neutron radiography. The generator makes an excellent fast, intermediate, and thermal neutron source for laboratories and industrial applications that require the safe production of neutrons, a small footprint, low cost, and small regulatory burden. The generator has three major components: a Radio Frequency Induction Ion Source, a Secondary Electron Shroud, and a Diode Accelerator Structure and Target. Monoenergetic neutrons (2.5MeV) are produced with a yield of 1010n/s using 25–50mA of deuterium ion beam current and 125kV of acceleration voltage. The present study characterizes the performance of the neutron generator with respect to neutron yield, neutron production efficiency, and the ionic current as a function of the acceleration voltage at various RF powers. In addition the Monte Carlo N-Particle Transport (MCNP) simulation code was used to optimize the setup with respect to thermal flux and radiation protection.

Ultrasound generation with high power and coil only EMAT concepts

Electro-magnetic acoustic transducers (EMATs) are intended as non-contact and non-destructive ultrasound transducers for metallic material. The transmitted intensities from EMATS are modest, particularly at notable lift off distances. Some time ago a concept for a “coil only EMAT” was presented, without static magnetic field. In this contribution, such compact “coil only EMATs” with effective areas of 1–5cm2 were driven to excessive power levels at MHz frequencies, using pulsed power technologies. RF induction currents of 10kA and tens of Megawatts are applied. With increasing power the electroacoustic conversion efficiency also increases. The total effect is of second order or quadratic, therefore non-linear and progressive, and yields strong ultrasound signals up to kW/cm2 at MHz frequencies in the metal. Even at considerable lift off distances (cm) the ultrasound can be readily detected. Test materials are aluminum, ferromagnetic steel and stainless steel (non-ferromagnetic). Thereby, most metal types are represented. The technique is compared experimentally with other non-contact methods: laser pulse induced ultrasound and spark induced ultrasound, both damaging to the test object’s surface. At small lift off distances, the intensity from this EMAT concept clearly outperforms the laser pulses or heavy spark impacts.

Growth of threaded AlN whiskers by a physical vapor transport method

Threaded aluminum nitride (AlN) whiskers are grown by a physical vapor transport method in a radio-frequency induction heating furnace. The resultant whiskers are characterized by X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy and photoluminescence. The analysis shows that the whiskers are single-crystalline, wurtzite AlN. The threaded AlN whiskers are 0.5 μm∼100 μm in diameter and several millimeters in length in the fiber direction, and have lots of tiny sawteeth on the surface. The morphology of this threaded AlN whisker is beneficial for bonding when the whisker is used in composite. The growth of the whiskers is dominated by the vapor—solid (VS) mechanism, and the particular morphology might result from an oscillating condition produced in the radio-frequency induction heating furnace.

RF 유도결합 열 플라즈마를 이용한 암모니아와 질소분위기에서 고순도 AlN 나노 분말의 합성

High-purity aluminum nitride nanopowders were synthesized using an RF induction thermal plasma instrument. Ammonia and nitrogen gases were used as sheath gas to control the reactor atmosphere. Synthesized AlN nanopowders were characterized by XRD, SEM, TEM, EDS, BET, FTIR, and N-O analyses. It was possible to synthesize high-purity AlN nanoparticles through control of the ammonia gas flow rate. However, additional process parameters such as plasma power and reactor pressure had to be controlled for the production of high-purity AlN nanopowders using nitrogen gas.

Preparation of spherical tungsten and titanium powders by RF induction plasma processing

Spherical tungsten and titanium powders were prepared by radio frequency inductively coupled plasma torch with irregular shaped tungsten and titanium hydride (TiH2) powders, respectively. The effect of the feed rate on spheroidization efficiency was investigated. The phase composition, oxygen content, morphology, and particle size distribution of the powders before and after spheroidization were characterized by X-ray diffraction (XRD), nitrogen/oxygen analyzer, scanning electron microscopy (SEM), and laser micron sizer (LMS). The results show that both kinds of plasma-processed powders have good dispersity, smooth surface, and single phase. A maximum of 100 % of spheroidization efficiency can be achieved at a lower feed rate. The spherical titanium powder obtained by the plasma treatment consists of particles with mean diameter of 33.34 μm, while the mean diameter of original TiH2 powder is 136.56 μm. The apparent density and flowability of the spherical tungsten powder are 6.3 g·cm−3 and 0.16 s·g−1, respectively. The apparent density and flowability of the spherical titanium powder are 2.8 g·cm−3 and 0.52 s·g−1, respectively. With the increase of the feed rate, the spheroidization efficiency of raw powders drops gradually.

Synthesis of nanostructured MgO powders with photoluminescence by plasma-intensified pyrohydrolysis process of bischofite from brine

Abstract Nanostructured MgO powders were synthesized by an ultra-high temperature pyrohydrolysis process of bischofite (MgCl2·6H2 O) in a radio frequency (RF) induction thermal plasma system. The structure, morphology and optical properties were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results showed that MgO nanopowders with two different morphologies were fabricated: near spherical MgO nanoparticles with size in the range of 20∼40 nm and 1D nanobelts with a width of about 100 nm. The photoluminescence (PL) studies showed that both of these two kinds of nanostructured MgO powders exhibited a strong ultraviolet-green PL emission under the excitation of 325 nm He-Ne laser.

Study on Two Plasma Physical Vapor Deposition Methods for Preparing Ultrafine Al Powders

Plasma physical vapor deposition method was most widely used to prepare ultrafine Al powders. Direct Current Arc Plasma (DCAP) and Radio Frequency Induction Plasma (RFIP) were adopted individually to produce Al powders with different particle size. The micro structure such as grain size, morphology and crystal phase was examined by SEM, TEM and XRD methods. The results show that the Al production by RFIP was better than by DCAP. DCAP has outstanding advantages in producing nanoAl powders with the particle size below 300nm while the RFIP is better to produce Al powders with the particle size 300nm to 1 μm.

Isothermal Bainite Transformation in Low Silicon TRIP Steel with Phosphorus Addition

The low silicon transformation-induced plasticity (TRIP) steel with phosphorus addition is consisted of the microstructure of retained austenite, ferrite and bainite which produced by intercritical annealing and isothermal bainite transformation followed by rapid cooling. In this study, isothermal bainite transformation of different experimental parameters in low silicon TRIP steel with phosphorus addition was investigated in laboratory. The addition of cheap element phosphorus, which has the same effect of silicon in retard the kinetics of carbide formation during isothermal bainite transformation, can reduce the silicon content, improve surface quality, solve galvanizing problem and reduce costs. The effect of bainite isothermal temperature, intercritical annealing temperature and heating rates were investigated by dilatometric experiment on a push-rod Formastor-FII high-speed dilatometer with radio frequency induction heating. The high resolution observations, composition analysis and elements distribution of microstructure were carried out using the electron scanning microscopy of a field emission electron probe microanalyzer (JEOL JXA-8530F) operating at 20KV accelerating voltage.

유도결합 열 플라즈마를 이용한 고순도 질화알루미늄 나노 분말 합성

질화알루미늄(AlN)은 뛰어난 열적, 전기절연성 특성을 갖고 있어 반도체 기판용 재료나 전자 패키징 재료로 주목받고 있다. 질화알루미늄은 소결온도가 높고 불순물로 인한 물성저하 때문에 고순도화 및 나노원료화가 필수적이다. 본 연구에서는 RF 유도결합 열플라즈마를 이용하여 알루미늄 분말로부터 고순도의 질화알루미늄 나노분말을 합성하였다. Sheath gas로 사용된 암모니아의 유량 제어를 통해 고순도의 질화알루미늄 나노분말이 합성되는 조건을 확립하고자 하였으며 합성된 분말은 XRD, SEM, TEM, BET, FTIR, N-O분석을 통해 특성분석을 진행하였다. Aluminum nitride, which has outstanding properties such as high thermal conductivity and electrical resistivity, has been received a great attention as a substrate and packaging material of semiconductor devices. Since aluminum nitride has a high sintering temperature of 2173 K and its properties depends on the impurity level, it is necessary to synthesize high-purity and nano-sized aluminum nitride powders for the applications. In this research, we synthesized high purity aluminum nitride nanopowders from aluminum using RF induction thermal plasma system. Sheath gas (NH3) flow was controlled to establish the synthesis condition of high purity aluminum nitride nanopowders. The obtained aluminum nitride nanopowders were evaluated by XRD, SEM, TEM, BET, FTIR and N-O analysis.