Intense Pulsed Ion-beam Evaporation Research Articles

Structures and photoluminescence properties of silicon thin films prepared by pulsed ion-beam evaporation

Synthesis of photoluminescent (PL) Si thin films is explored using an intense pulsed ion-beam evaporation (IBE) technique. The deposition of Si was performed at a vacuum condition of ∼10 −2 Pa in a simple scheme. Well-crystallized Si thin films have been obtained as revealed by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). Visible light emission in blue–green range was observed from the samples under excitation of a 325 nm He–Cd laser (3.8 eV) at room temperature. The thin films were composed of relatively large crystals with an average size around 20 nm, above the range predicted using a quantum confinement model proposed for Si nanocrystals. The PL was subsequently studied with a hydrofluoric acid (HF) erosion test, intended to diminish the effect of Si oxides on the samples, where no PL shift was found except for deterioration in PL intensity after the post-treatment of samples. Furthermore, the experimental PL spectra can be consistently deconvolved into four subbands with centers at 2.88, 2.75, 2.55, and 2.36 eV. All the PL subbands are ascribed to Si oxide-defect bands irrelevant to the quantum confinement model.

Preparation of silicon nanoparticles for device of photoluminescence

We experimentally demonstrated the synthesis of silicon nanoparticles by using high-density ablation plasma prepared by the interaction of an intense pulsed light-ion beam with a target, known as the intense pulsed ion beam evaporation method. Blue light emission was obtained from the silicon nanoparticles. It was determined that the ambient gas reaction is very important and useful method to obtain the photoluminescence from the silicon nanoparticles.

Preparation of silicon thin films by intense pulsed ion-beam evaporation method with low temperature process

We have succeeded in preparing polycrystalline silicon thin films by the intense pulsed ion-beam evaporation method without impurities on substrates of silicon and quartz. Good crystallinity and high deposition rate were achieved without thermal processing such as heating the substrates. The crystallinity of poly-Si film has been improved by increasing the density of the ablation plasma. Since the lifetime of the ablation plasma, which was obtained by a pulsed ion beam with 50-ns pulse width, is of the order of 20 μs, the instantaneous deposition rate is in the region of cm/s. The crystallinity was increased by increasing the number of shots. The crystallization and the deposition rate of poly-Si thin films prepared on different substrate positions were investigated.

Synthesis of Light-emitting Silicon Nanoparticles by Intense Pulsed ion-beam Esvaporation

Synthesis of photoluminescent Si nanoparticles has been successfully prepared using an intense pulsed ion-beam evaporation (IBE) technique in vacuum. Si nanoparticles are produced by the IBE method without any post-annealings. Photoluminescence (PL) mainly in blue range with a peak of 455 nm and a shoulder near 510 nm is observed in as-deposited Si nanoparticles at room temperature. The blue light emission is relatively stable with no noticeable change, as the samples have already stored in air more than 4 months. The observed PL does not fit the quantum confinement model, since a majority of particle size is around ~20 nm, estimated by SEM and XRD measurements. Moreover, hydrofluoric acid (HF) corrosion tests on the Si nanoparticles also indicate a correlation between the presence of the surface oxide layers and the PL. Oxide-related luminescence is likely the source of this blue light emission.

Room Temperature Preparation of Poly-Si Thin Films by IBE with Substrate Bias Method

Using intense pulsed ion beam evaporation technique, we have succeeded in the preparation of poly crystalline silicon thin films without impurities on silicon substrate. Good crystallinity and high deposition rate have been achieved without heating the substrate by using lEE. The crystallinity of poly-Si film has been improved with the high density of the ablation plasma. The intense diffraction peaks of poly-Si thin films could be obtained by using the substrate bias system. The crystallinity and the deposition rate of poly-Si thin films were increased by applying (-) bias voltage for the substrate.

Extinction of Large Droplets in Ion-Beam Ablation Plasma Produced by Ion-Beam Evaporation

The extinction of large droplets in ablation plasma produced by intense pulsed ion-beam evaporation (IBE) has been proposed to improve the surface morphology of Al thin films on Si substrates. After the ion-beam irradiation of an Al target, a lot of spherical objects with diameters of approximately 20 to 100 µm were observed on the Al target surface, they are considered to be a possible origin of droplets commonly observed on Al thin films. However, the number of large droplets decreased with increasing distance between the Al target and Si substrate. The following model was considered to explain the obtained results. When a spherical object flies in the ablation plasma, it seems that the object fragments into small pieces or is evaporated. As a result, the number of large droplets decreases with increasing flight distance.

Thermoelectric properties of boron-carbide thin film and thin film based thermoelectric device fabricated by intense-pulsed ion beam evaporation

Crystallized B13C2 thin films were fabricated by intense pulsed-ion beam evaporation (IBE) method. Electrical conductivity and Seebeck coefficients of the obtained films were 1×10—4 l/Ωm and 200 μV/K at 1000 K, respectively. These values were comparable to those of bulks. For the application of the thin films, since reasonable thermoelectric (TE) properties were confirmed for the B13C2 films fabricated, we attempted to develop ’in-plane’ type TE device using B13C2 and SrB6 as p-type and n-type elements, respectively. With applying temperature difference to the fabricated device, thermo-electromotive force and electrical power were generated from the device we made, indicating that the device worked as a TE device. To the best of our knowledge, this is the first demonstration of the TE device composed of only boron-rich solids.

Defect-related photoluminescence of silicon nanoparticles produced by pulsed ion-beam ablation in vacuum

Visible light emission has been observed from Si nanoparticles produced using an intense pulsed ion-beam evaporation (IBE) technique in vacuum. The as-prepared Si nanoparticles possess good crystallinity without any post-annealing. Room-temperature photoluminescence (PL) spectra for the Si nanoparticles were registered in blue–green range. The average crystal size (around 20 nm) estimated from glancing angle X-ray diffraction (GAXRD) was relatively large, inconsistent with quantum size effect for the light emission. The Si nanoparticles was exposed to O 2 gas at elevated temperature and hydrofluoric acid (HF) vapor at room temperature for examining the PL source, where significant deterioration of PL intensity was found subsequently. Combined with analyses of X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX), the PL is attributable to oxide defects of the samples.

Preparation of TiFe thin films by intense pulsed ion-beam evaporation

Titanium iron (TiFe) is widely known as an intermetallic compound that shows hydrogen storage characteristics. In the past, preparation of Ti–Fe thin films has been tried by sputtering methods, but crystallized thin films have not been prepared yet. The preparation of crystallized TiFe thin films has been attempted by intense pulsed ion-beam evaporation in which a Ti–Fe sintered compact (Ti–50 at.% Fe, Ti–40 at.% Fe) was used as a target. Using the T–50 at.% Fe target, thin films deposited on soda lime glass substrate have been found to be mixed phases of TiFe and TiFe 2. Thin films deposited on Si(100) substrates consist of an amorphous phase. Using a Ti–40 at.% Fe target, a thin film of single-phase TiFe has been successfully prepared on glass substrate. The crystallized, single-phase TiFe thin film is believed to be the first obtained in the world.

Characteristics of polycrystalline silicon thin films prepared by pulsed ion-beam evaporation

Using the intense pulsed ion-beam evaporation method, we have succeeded in preparing polycrystalline silicon thin films without impurities on substrates of silicon and quartz. High crystallinity and deposition rate were achieved without heating the substrate. Since the lifetime of the ablation plasma, which was obtained by a pulsed ion beam with 50-ns pulse width, is of the order of 20 μs, the instantaneous deposition rate is in the region of cm/s. The crystallinity of poly-Si film has been improved by increasing the density of the ablation plasma, whereby the grain size of the film was found to be smaller.

Preparation of polycrystalline silicon thin films by pulsed ion-beam evaporation

Using the intense pulsed ion-beam evaporation technique, we have succeeded in the preparation of polycrystalline silicon thin films. Good crystallinity and high deposition rates have been achieved without substrate heating. The crystallinity of poly-Si film has been improved by increasing the density of the ablation plasma. The intense diffraction peaks and high density of poly-Si thin films can be obtained by biasing the substrate.

Luminescent Properties of SrAl2O4:Eu Thin Films Deposited by Intense Pulsed Ion-Beam Evaporation

SrAl2O4 activated with Eu, a long-phosphorescence material with high brightness, has been successfully deposited on Si substrates using intense pulsed ion-beam evaporation. Efficient preparation of long-phosphorescence thin films has been achieved using a high-density ablation plasma produced by the interaction of an intense pulsed ion-beam with the SrAl2O4:Eu target. The prepared SrAl2O4:Eu thin films had a polycrystalline structure without annealing and showed a typical photoluminescence of SrAl2O4:Eu at around 520 nm. Thermoluminescence (TL) measurements were carried out in order to obtain the lifetimes of the phosphorescence. In particular, TL spectra in the higher temperature region, which contributed to the long phosphorescence, were examined by the partial heating technique to evaluate the distributed trap depths and the lifetimes. The phosphorescence lifetime at 300 K for the prepared film was found to be about 180 min.

Synthesis of Ti–Al Intermetallic Compound Films by Intense Pulsed Ion Beam Evaporation

In order to examine the possibility of the synthesis of an intermetallic compound thin film by intense, pulsed, ion beam evaporation (IBE), the synthesis of thin films of Ti–Al system intermetallic compound was attempted. The crystal structure and composition of the films were evaluated. By using a combination target of Ti and Al, thin films of single phase could not be synthesized, while the Ti3Al film was found to be successfully synthesized by using a Ti/Al sintered target. The Ti3Al film was orientated in the 002 plane.

Ferroelectric Thin Films Prepared by Backside Pulsed Ion-Beam Evaporation

Ferroelectric (PbTiO3 or Pb(Zr, Ti)O3) thin films have been successfully prepared on Si(100) or pyrex glasses by backside deposition of intense pulsed ion beam evaporation. The ion beam parameters were typically as follows: beam energy=1.3 MeV, ion-current density on target=0.7 kA/cm2 and pulse duration=50 ns. The composition of the thin films was in good agreement with that of the original target. The relative dielectric constant at 1 kHz was obtained to be 20, while that obtained by normal front side deposition was 150.

Preparation of SrAl2O4:Eu Phosphor Thin Films by Intense Pulsed Ion-Beam Evaporation

SrAl2O4 activated with Eu phosphors has been known to exhibit high brightness and long-lasting phosphorescence without radioactive materials. In this paper, SrAl2O4:Eu thin films have been successfully deposited on Si(100) or graphite substrates using an intense pulsed ion-beam evaporation technique. The results of X-ray diffraction and photoluminescence suggest that SrAl2O4:Eu thin films which have a polycrystalline structure can be produced in vacuum, without substrate heating and annealing. The composition and morphology of the films have been analyzed by Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM). From RBS analysis, we have obtained good stoichiometry between the target and the films prepared.

Preparation of B4C Thin Film by Intense Pulsed Ion-Beam Evaporation

Boron carbide (B4C) is known as a material having hardness, wear resistance and stability at high temperature. The preparation of thin films of B4C, therefore, is very important from the viewpoint of industrial applications. We have experimentally attempted to prepare thin films of B4C using the pulsed ion-beam evaporation (IBE) technique, where high-density ablation plasma is produced by an intense pulsed ion beam interaction with the target. The crystallized B4C thin films have been successfully deposited on a Si (100) substrate by front-side and mask-side deposition. Absorptions associated with the B–C combination and the vibration of B12–B12 clusters have been observed by Fourier transform infrared spectroscopy. The Vickers hardness of the film deposited by front-side deposition is observed to be HV∼2300.

Novel Preparation Method of Thin Films by Ablation Plasma produced by Intense Pulsed Ion Beam Evaporation

AbstractA novel preparation method of thin films has been successfully developed by high-density ablation plasma produced by pulsed ion-beam evaporation method. The preparation is available with extremely high deposition rate (with cm/s), without heating the substrate, in a vacuum, with good stoichiometry. As an example, the preparation of phosphoresecent SrAl2O4:Eu, Dy thin films will be shown. Furthermore, a new method has been developed of the synthesis of ultrafine nanosize powders by use of microexplosion of pulsed wire discharge. As an example, the synthesis of NiFe2O4 powders will be shown, where two wires of nickel and iron were exploded by pulsed current. In addition, we have succeeded in the preparation of tungsten thin films within via holes in LSI by use of pulsed ion beam-evaporation method. In addition to the huge power per shot, a new machine has been developed of highly repetitive, pulsed power machine for the industrial applications.

Characteristics of Polycrystalline Silicon thin Films Prepared by Pulsed Ion-Beam Evaporation

AbstractUsing intense pulsed ion-beam evaporation technique, we have succeeded in the preparation of polycrystalline silicon thin films on silicon substrate without impurities. Good crystallinity and high deposition rate have been achieved without heating the substrate. The crystallinity of poly-Si film has been improved with increasing the density of the ablation plasma. The intense diffraction peaks of poly-Si thin films can be obtained by using the substrate bias system. The crystallinity and the deposition rate of poly-Si thin films are increased by negative bias voltage for the substrate.

大強度パルスイオンビーム蒸着法によるアブレーションプラズマの動特性評価

大強度パルスイオンビーム蒸着法によるアブレーションプラズマの動特性評価