Reactive sputtering of luminescent YAG:Ce thin films by dual hollow cathode plasma-jet

The Dual hollow cathode plasma source uses hollow cathode cylindrical sputtering and ionizing metal elements, which has a high material utilization rate and has potential application in the field of material modification. Its performance index requires the cooperation of electrode discharge parameters and the rational utilization of the inner surface of the hollow cathode. In this paper, a two-dimensional fluid model of a Dual hollow cathode structure is developed to simulate the basic distribution of the Dual hollow cathode discharge, which fills the central region of the Dual hollow cathode structure and the electrons oscillate on the axis. The effects of electrode parameters and hollow cathode radius on the discharge were investigated. The results show that the radial electron density of the hollow cathode increases with increasing heated cathode voltage, but as the hot cathode voltage continues to expand beyond 1200 V this trend becomes less obvious. The enhancement of the wall ion current by the heated cathode voltage is very pronounced, and the hollow cathode discharge is the result of the mutual enhancement of the heated cathode voltage and the hollow cathode voltage. Hollow cathode sputtering needs to reach a voltage threshold of 300 V, and the existence of an optimal radius (r = 4 mm−6 mm) to achieve a high plasma density and at the same time favor hollow cathode sputtering.

A new design for a dual hollow cathode arc chemical vapor deposition system is used to grow diamond films. The inner hollow cathode is the primary thermionic emission source. The outer hollow cathode magnified the discharge current. Contrary to the single hollow cathode chemical vapor deposition, the dual hollow cathode chemical vapor deposition can deposit diamond films free of cathode contaminants, and therefore, enhance the film quality. With the aid of electron bombardment of the substrate, the dual cathode design can grow diamond films of good crystalline quality, and with a high growth rate, 2.3 µ/h, even at a high CH4 concentration such as 10% and at a low pressure of 15 Torr.

Experimental results on thin films of the new material Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x </sub> C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> , deposited by a unique dual plasma hollow cathode sputtering technique are presented. The GeC films grown on etched Si (100) exhibited remarkable crystallinity with a lattice spacing very near that of Si. This order has been characterized using X-ray diffraction (XRD) and Raman spectroscopy. The deposition rate ratio of Ge to C did not have a great effect on the crystallinity nor on the presence or absence of Ge-C lattice bonds. However, the substrate type had a great influence. Although microcrystalline films of GeC were grown on oxidized Si surfaces, the Ge-C lattice bond did not appear to be present in all cases though it was for films grown on Si etched with HF. The photon absorption for these films was greater than that for pure Si and for pure Ge. This promising result indicates that this material has potential for future photovoltaic devices

Structural and luminescent properties of YAG:Ce thin film phosphor

Magnetic properties of low-temperature grown Si:Ce thin films on (0 0 1) Si substrate

The ZnO and ZnO:Ce thin films were prepared by DC reactive magnetron sputtering. The structure, surface morphology, optical and photoluminescence properties of ZnO:Ce thin films were investigated. The XRD results indicated that all the samples exhibited a hexagonal wurtzite structure. The surface morphology of the films was sensitive to the Ce concentration. All the films had a higher average transmittance (more than 85%) in the visible region and a strong absorption near the band-edge of ZnO. The photoluminescence properties of the Ce-doped ZnO thin films were also studied. Blue emissions were observed from the ZnO:Ce thin films. Our results indicated that the photoluminescence properties of ZnO thin films doped with low Ce concentration were related to the intrinsic transition of Ce3+ ions. However, when the Ce concentration increased, Zni also played an important role.

Bi(1−x)Ce x Fe(1−x)(Mg0.5Ti0.5) x O3 (x = 0, 0.05, 0.10, 0.20, 0.25) thin films were synthesized by a sol–gel method. The structural, electrical and magnetic properties of Bi(1−x)Ce x Fe(1−x)(Mg0.5Ti0.5) x O3 (x = 0, 0.05, 0.10, 0.20, 0.25) thin films have been investigated. BiFeO3 thin film possessed a perovskite-type rhombohedral structure with space group R3c, and the average grain size decreased as the concentration of Ce, Mg and Ti co-doping increased. The leakage current densities of BiFeO3 co-doping with Ce, Mg and Ti ions exhibited a significant reduction compared with that of BiFeO3 thin film. Compared with the leakage current density of BiFeO3 thin film (4.19 × 10−4 A/cm2), the leakage current density of Bi0.80Ce0.20Fe0.80Mg0.10Ti0.10O3 thin film was reduced by about four orders of magnitude (1.05 × 10−8 A/cm2) under the electric field of 300 kV/cm. Well-defined ferroelectric loops were obtained and the polarization increased with the increase of Ce, Ti and Mg co-doping. The remanent polarization of Bi0.80Ce0.20Fe0.80Mg0.10Ti0.10O3 thin film (2P r ~34.9 μC/cm2) was approximately four times larger than that of pure BiFeO3 (2P r ~7.8 μC/cm2) under the applied field of 300 kV/cm. The magnetization under 10 kOe magnetic field of Bi(1−x)Ce x Fe(1−x)(Mg0.5Ti0.5) x O3 thin films increased with the increasing concentration of Ce, Mg and Ti co-doping. The improvement of magnetic behaviors for BiFeO3 co-doping with Ce, Mg and Ti ions thin films were observed significantly, cooperating with the enhanced ferroelectricity which indicated that BiFeO3 co-doping with Ce, Mg and Ti ions thin films will be the promising materials in the application to magnetoelectric devices.

Preparation and luminescent properties of SrSe:Ce thin films

A diluted magnetic semiconductor, Si:Ce thin films with the Ce concentration below 4.3 at%, were prepared by solid source molecular beam epitaxy. The lattice constant of the Si:Ce film increases with increasing the Ce concentration, while it decreases above Ce 0.2 at%. Magnetization measured at 4.2 K for the samples with the Ce concentration up to 0.2 at% also increases with increasing the Ce concentration up to 0.2 at%. The amount of substituted Ce in Si is considered to play an important role for the magnetic properties.

Low temperature growth of Si:Ce thin films with high crystallinity and uniform distribution of Ce grown by solid-source molecular beam epitaxy

SrS:Ce thin films were prepared on several kinds of insulating underlayers, Ta2O5, SiO2, Si3N4 and their composite films, by hot wall deposition. The crystallinity of the SrS:Ce films was found to depend strongly upon the underlayers, although no crystal structures were confirmed for the underlayers. The SrS:Ce films grown directly on Ta2O5 layers gave the best crystallinity, and better luminance levels were also obtained for their electroluminescent devices, due to both the large dielectric constant of Ta2O5 and good crystallinity of the SrS:Ce films.

The dual hollow cathode ion source for metal ion beams (Duhocamis) was introduced in 2007. The Duhocamis is derived from the indirectly-heated cathode GSI-PIG ion source and more suitable for producing various metal ion beams. To further understand the discharge characteristics of Duhocamis, a series of arc discharge experiments have been performed on the test bench at Peking University. The transfer process from PIG discharge to dual hollow cathode discharge (DHCD) mode in the source was observed by changing the sputter voltage, and the metal ion ratio of > 90% for DHCD was measured. The formation process of metal plasma is emphasized and discussed in this article.

Photoluminescence in sol–gel-derived YAG:Ce phosphors

The effects of substrates and deposition parameters on the growing and luminescent properties of Y3Al5O12:Ce thin films

Magnetic properties and the chemical bonding state of Ce for a diluted magnetic semiconductor (DMS), n-type Si:Ce thin films with a Ce concentration below 8.0 at. % grown by low-temperature molecular beam epitaxy (LT-MBE) are investigated. LT growth enables the films to have a uniform distribution of Ce in epitaxial Si films with a Ce concentration up to 8.0 at. %. The precipitation of the second phase, such as cerium silicide, is not recognized in the film with a Ce concentration of 4.0 at. % by electron diffraction using transmission electron microscopy (TEM) analysis. All the films exhibit n-type conduction. The electron density increases with increasing Ce concentration up to 0.07 at. % because of the generation of electrons by point defects. Then, the density decreases with increasing Ce concentration up to 1.1 at. % because of the compensation by the hole generated by substitutionally dissolved Ce3+. A positive magnetization due to a Ce3+ ion is observed in all the films. Unlike p-type Si:Ce, however, ferromagnetic or super-paramagnetic behavior is not observed in uniformly Ce-doped Si films with n-type conduction, suggesting that the hole plays an important role in the anomaly observed in magnetotransport behaviors in Ce-doped Si films.