Metal Vapor Atoms Research Articles

Simulation of lutetium metal evaporation with considering atomic metastable state

Lutetium-177, one of the current global research hotspots for medical isotopes, can be produced by reactor irradiation of lutetium-176, which can be produced and processed with the assistance of the electron beam physical vapor deposition (EB-PVD). The metal evaporation process is an important part of EB-PVD, which aims to convert solid metal into metal atomic vapor. The distribution of each macroscopic characteristic quantity, such as thermal population distribution, density distribution, velocity distribution, and temperature distribution of metal atomic vapor, will directly affect the utilization of metal vapor atoms, the subsequent deposition process, and coating process. In this paper, two-dimensional model and three-dimensional model of the metal evaporation process are established based on the direct simulation Monte Carlo method, and atomic metastable state is introduced into the collision assumption. The macroscopic characteristic quantities, such as the number density of metal atomic vapor, the motion velocity and the discrete degree of the total motion velocity in the evaporation process with or without considering the lutetium atomic metastable state, are analyzed and compared. The spatial distribution characteristics of each energy level of metal atomic vapor are observed, and the variation characteristics of the macroscopic characteristic quantities in the center with the slit opening size and the evaporation source surface temperature are discussed. The study results show that the number density of metal vapor passing through the beam flow device decreases, the average velocity in the <i>x</i>-direction and <i>z</i>-direction and the discrete degree of the total motion velocity increase, with the atomic metastable state taken into consideration. The beam flow device intensifies the transformation of the atomic energy level of the metal vapor and changes the physical parameters of the metal atomic vapor. At the same time, the slit opening size and the evaporation source surface temperature trigger off the change of the macroscopic characteristic quantity distribution of the metal vapor, including the degree of anomalous protrusion of each macroscopic characteristic quantity above the slit. The results of the three-dimensional simulation based on the two-dimensional model are consistent with the changes in the order of magnitude of data distribution and spatial distribution pattern, which can serve as a reference and guidance for the experimental study of the electron beam metal evaporation process.

Nucleation mechanism of metal-vapor atoms on photochromic diarylethene surface with a low glass transition temperature

Metal pattern formation on organic surfaces is essential in organic electronics. Selective metal-vapor deposition using photochromic diarylethene (DAE) is a promising method to prepare fine metal patterns by maskless evaporation. Metal-vapor atoms are adsorbed, diffused, and then desorbed from the colorless surface with a low glass transition temperature. We, however, found that metal deposition started at a specific time (deposition-threshold time, tth) even on the colorless surface by continuous evaporation. tth was investigated using a quartz crystal microbalance. We elucidated that metal-nucleation sites were generated by chemical reactions between metal atoms and surface DAE molecules. The number of nucleation sites increases during metal evaporation and when the sites are located in the diffusion range of surface metal atoms, metal-atom nucleation for film-formation starts. This is the origin of tth. This result would provide important knowledge for the preparation of electrodes for organic devices based on selective metal-vapor deposition.

Nucleation, absorption, or desorption of metal-vapor atoms on amorphous photochromic diarylethene films having a low glass transition temperature

Metal-vapor atoms with high or low intrinsic vapor-pressure were absorbed into or desorbed from the low-Tg colorless photochromic film, respectively.

Indirect pumping bell–bloom magnetometer**Project supported by the Natural Science Foundation of Shanghai (Grant No. 16ZR1402700), the National Natural Science Foundation of China (Grant No. 91636102), and the National Key Research and Development Program of China (Grant No. 2016YFA0302000).

When the ground state hyperfine splitting of alkali metal vapor atoms is well optically resolved, the spin coherence on one hyperfine sublevel can be generated directly or indirectly by pumping the same or the other sublevel respectively. We experimentally studied the pump power dependence of the field response of a Bell-Bloom magnetometer for the two pumping schemes in a paraffin coated 87Rb vapor cell. We find that although the maximum field response is achieved by combining the two pumping schemes, indirect pumping alone can do nearly as good while being much simpler to operate. We have achieved a sensitivity of 100 fT/Hz1/2 with a single indirect pump at room temperature.

Metal-vapor integration/transportation based on metal-atom desorption from polymer surfaces with a low glass-transition temperature

Vacuum evaporation, which is widely used to obtain a metal-film coating on substrates and/or targets, results in a large loss of evaporation materials. The authors discovered a selective metal-vapor deposition phenomenon in which metal-vapor atoms can be deposited selectively without a shadow mask. The core phenomenon of selective deposition is the desorption of metal-vapor atoms from organic surfaces with a low-glass transition temperature (low-Tg). The authors investigated metal-atom desorption from low-Tg polymer [polydimethylsiloxane (PDMS)] surfaces during vacuum deposition and found that greater than 2-μm-thick PDMS film enables high desorption efficiency. The authors proposed two vacuum deposition methods: metal-vapor transportation and metal-vapor integration. The former method attained reduced substrate surface temperatures during vacuum evaporation and the latter enabled extremely high deposition efficiency and three-dimensional deposition in a one-batch process. These new methods can greatly widen applications of vacuum deposition.

Selective Metal-vapor Deposition on Organic Surfaces.

Selective metal-vapor deposition signifies that metal-vapor atoms are deposited on a hard organic surface, but not on a soft (low glass transition temperature, low Tg ) surface. In this paper, we introduce the origin, extension, and applications of selective metal-vapor deposition. An amorphous photochromic diarylethene film shows light-controlled selective metal-vapor deposition, which is caused by a large Tg change based on photoisomerization, but various organic surfaces, including organic crystal and polymers, can be utilized for achieving selective metal-vapor deposition. Various applications of selective metal-vapor deposition, including cathode patterning of organic light-emitting devices, micro-thin-film fuses, multifunctional diffraction gratings, in-plane electrical bistability for memory devices, and metal-vapor integration, have been demonstrated.

Selective metal deposition on organic surfaces for device applications

Selective metal deposition signifies that metal vapor atoms are deposited on a hard organic surface but not on a soft (low glass transition temperature) surface. This paper introduces the origin, extension, and device applications of selective metal deposition. A photochromic surface shows the light-controlled selective metal deposition phenomenon, but the surface material is not essential to it; various organic surfaces including organic crystal and polymer surfaces can be used. We demonstrate the applications of selective metal deposition, including cathode patterning for organic light-emitting devices, micro thin-film fuses, and multifunctional diffraction grating. Selective metal deposition can be applied to a variety of electric and optic devices.

Metal-vapor deposition modulation on polymer surfaces prepared by the coffee-ring effect

We report a novel function of a polymer coffee-ring surface called metal-vapor deposition modulation where metal-vapor atoms are deposited on the center of the polymer coffee-ring surface using vacuum evaporation but not on the ring-shaped areas at the edge. The essential factor of the metal-deposition modulation is the difference of polymer chain mobility between the center and the ring. In the ring, the solvent evaporation process produces large spaces among surface polymer chains, resulting in high mobility of polymer chains. The desorption of metal vapor atoms from the surface was caused by the high mobility of the polymer chains. This result not only provides new knowledge about the fundamentals of a polymer surface but also suggests a novel technology for engineering and industrial fields using metallic coating technology on polymer surfaces.

Size Focusing of Nanoparticles by Thermodynamic Control through Ligand Interactions. Molecular Clusters Compared with Nanoparticles of Metals.

Ligand-capped metal entities come in two sizes, (1) molecular clusters of 10-200 metal atoms and (2) nanoparticles of 2000-10000 metal atoms. In numerous cases, certain "magic sizes" have been found to be most accessible and stable, clusters of 25, 38, 55, and 102 atoms and nanoparticles of 3500-5000 atoms or 4-5 nm. The most familiar and studied system is that of gold (metal) and thiol (ligand). Herein, the methods of synthesis of these gold clusters versus gold nanoparticles are carefully compared. In the cluster case, an important intermediate is the (Au(+)SR(-))n polymer, which is not the case in the synthesis of nanoparticles either from metal (vapor) atoms or metal ions. Also, it is shown that thiol can act as both a reductant (Au(3+) → Au(+)) and as an oxidant (Au(0) → Au(+)). The thermodynamic forces responsible for the favored formation of certain size clusters and nanoparticles are discussed.

Light-Controlled Selective Metal Deposition on a Photochromic Diarylethene Film—Toward New Applications in Electronics and Photonics—

Abstract Selective metal deposition controlled by light irradiation was achieved for Zn, Mg, and Mn on a photochromic diarylethene (DAE) film; metal vapor atoms were deposited only on the colored film but not on the uncolored film. The deposition properties of the metals were strongly dependent on the deposition rates. Fine metal patterns were produced by laser scanning and a conventional vacuum-evaporation method without a shadow mask. Multiple-metal pattern preparation of Zn, Mg, and Mn via a maskless evaporation in a single vacuum process was also demonstrated.

Experimental and theoretical studies of metal vapor atoms

Employing electron spectrometry in conjunction with tuneable synchrotron radiation, we will present a detailed examination of the photoionization dynamics of selected metal vapor atoms. In particular, this paper will focus on the relative partial cross sections of the atomic Li K-shell main and satellite (ionization with excitation) photoelectron lines in the region of the strong 1 snℓ n′ℓ′ autoionizing transitions, the atomic Sc 3 d, 4 s main and satellite photoelectron lines in the region of the 3 p→3 d giant resonance, and also the atomic Fe 3 d, 4 s main and satellite photoelectron lines in the same resonance region. Our experimental data for Sc and Fe will be compared to our state-of-the-art calculations based on the superposition of configuration method developed by Cowan (The Theory of Atomic Structure and Spectra. University of California Berkeley Press, Berkeley and Los Angeles, 1981). Our partial cross section measurements for Li and Sc will be complemented with measurements of the angular distribution parameter, β. In addition, our Li data will also be compared with recent R-matrix calculations (Phys. Rev. 57 (1998) 1045). In the case of Fe, we will also address the term dependent behavior of the partial cross sections on resonance. These results will highlight what can be achieved with today's technology and point the way towards future endeavors in the study of the photoionization dynamics of open-shell metal vapor atoms.

Thin Film Deposition using a Velocity-Selected Vacuum Deposition Method. Development of Velocity Selector and Its Application to Vacuum Deposition.

In order to study the effects of the translational energy of incident metal atoms on the process of condensation and crystallization of thin films, we developed a method of vacuum deposition of velocity-selected metal-vapor atoms. A mechanical velocity selector for a neutral Ag beam was constructed and its performance was confirmed by measuring the velocity distribution of the velocity-selected beam. The velocity-selected vacuum deposition of Ag beam on (001) NaCl substrates reveals that the condensation coefficient of Ag on (001) NaCl depends greatly on the substrate temperature and that at the substrate temperature of 300°C it is much smaller than unity. Results also show that the effect of the deposition rate on crystalline structures is rather large and thin films deposited at a low deposition rate showed better epitaxial growth even at a lower substrate temperature.

Optical third-harmonic generation in alkali metal vapors

This paper considers third-harmonic generation in phase-matched mixtures of alkali metal vapors and inert gases. Calculations show that the combination of near-resonant nonlinear susceptibilities, the ability to phase match, and the relatively high UV transparency of these vapors should allow high conversion efficiency for picosecond laser pulses with a peak power of 108-109W. Calculations of the nonlinear susceptibility and of the ratio of xenon atoms to metal vapor atoms which is necessary to achieve phase matching are given for each of the alkalies as a function of incident laser wavelength. Processes that limit the allowable peak power density and energy density are discussed and guides for determining the metal vapor pressure, cell length, and beam area are given.

Electron beam image recorder

A new electron beam recording medium is reported. The medium is well suited for use in a high resolution recorder with near-real-time display capability. The development time can be less than 1 s. Black-on-white images are produced on the opaque tape with a contrast of 15:1 by exposure with 1 × 1011electrons/cm2for a peak density of 1.3. The resolution of the medium exceeds 500 line pairs/mm, and the granularity is very low. Another feature of the medium allows the recorded information to be read out directly from the tape with a scanning electron beam. The latent image is produced by a process termed nucleation. Electron bombardment of the tape produces nucleation sites which are extremely favorable deposition sites for metal vapor atoms. Development takes place in the vacuum, immediately after electron beam recording, by selectively depositing a thin metal film which forms the image. The developed image is permanent and does not degrade under further electron beam bombardment or high intensity projection lamps. Recordings of 945-line television with a 20 MHz bandwidth have been made with an electron beam recorder, which was constructed for evaluating the media. An opaque projector was also constructed for projecting 35 mm images from the tape to a large screen display.

NEW cw METAL-VAPOR LASER TRANSITIONS IN Cd, Sn, AND Zn

cw laser action has been observed at 3250 Å in Cd II, 6453 and 6844 Å in Sn II, and 7479 and 7588 Å in Zn II. Laser action occurred in He-metal-vapor discharges at pressures of several Torr He and much lower partial pressures of the metal vapor. The first four transitions have similar operating characteristics and are believed to be excited by Penning collisions between metastable He atoms and neutral metal-vapor atoms (similar to the mechanism for exciting the 4416 Å cw transition in Cd II). The 3250 Å transition is the first cw uv laser that can be built and operated with relatively simple techniques, similar to those used in He–Ne lasers.