Papers by Keyword: Secondary Ion Mass Spectroscopy (SIMS)

Abstract: In this paper, various annealing conditions using Al-based (Ti/Al/Ti/Au=70nm/100nm /5nm/120nm) and Ni-based (Ti/Ni/Ti/Au=20nm/90nm/5nm/120nm) metal contacts to n-type and p-type ion-implanted 4H-SiC epi layers have been studied in the effort to optimize simultaneous ohmic contact formation with the lowest specific contact resistance (SCR) values. Values of 1.091×10^-4 Ω∙cm² and 1.158×10^-5 Ω∙cm² were achieved using Al-based Ohmic metal contacts for p-type and n-type 4H-SiC, respectively, at an annealing temperature of 950°C and under vacuum for 90 sec. Ohmic formation mechanisms were analyzed using the X-Ray Diffraction (XRD) surface analysis method, indicating Ti₃SiC₂ alloys to be the key intermediate layer formed at SiC/Ti interface, responsible for Ohmic properties to p-type SiC. The paper summarizes the metal process combinations possible for the formation of Ohmic contacts to both n-type and p-type 4H-SiC, offering various options in either using the same metal materials and/or common annealing conditions.

Abstract: Secondary ion mass spectroscopy (SIMS) has been adopted to study the diffusion of Al and Si in Cu_44.25Ag_14.75Zr₃₆Ti₅ bulk metallic glass (BMG). It has been found that around the transition temperature of metallic glass, the relation between its diffusion coefficient and the temperature satisfy the same Arrhenius relation, which means the metallic transition has not caused change to the diffusion mechanism. In addition, the radius of Al atom is close to that of Si atom, but under the same temperature and time condition, the diffusion coefficient of Si atom in bulk metallic glass (BMG) is twice that of the Al atom, while there is not a big difference in diffusion activation energy. This is because as non-metallic element, the radius of Si atom has a strong binding force with the metal atoms in the base material, which also has a bigger diffusion coefficient.

Abstract: We had investigated the electromechanical coupling coefficient (K²) of surface acoustic wave (SAW) on proton-exchanged (PE) and annealed PE (APE) z-cut LiNbO₃ waveguides using octanoic acid. The penetration depth of hydrogen assumed to be equal to the waveguide depth (d) was measured by secondary-ion mass spectrometry (SIMS). The frequency response of SAW was measured with a network analyzer. The annealing process was carried out in a horizontal furnace kept at 400°C for 2 h under a dry O₂ gas flow. The change of K² in PE and APE samples fabricated under different conditions was dependent on kd, where k was the wavenumber. The experimental results showed that the variation of K² in PE samples was significantly decreased with the increase of kd. The reduction of K² may be due to the reduced piezoelectric coefficients in the PE layer. On the other hand, the variation of K² in APE samples also exhibited the decreased tendency after annealing. It indicated that the annealing process could not restore the reduction of K² caused by the PE process.

Abstract: To determine the effect of the annealing atmosphere on oxygen diffusion through Ba_0.95La_0.05FeO_3-d pellets, ¹⁸O₂ tracer diffusion and high-resolution secondary ion mapping were performed. When annealing in air, the ¹⁸O concentration around the surface up to a depth of 40 µm was almost constant. On the other hand, when annealing in vacuum, the ¹⁸O concentration obviously decreased. High-resolution secondary ion mapping indicated that the ¹⁸O concentration around the grain boundary was reduced. These results suggested that the grain boundary of BLF annealed in vacuum prevents oxygen diffusion.

Abstract: The relationship between Al and Li during diffusion was studied using Al-implanted ZnO. The Al donor in ZnO acts to increase the concentration of Li contamination from the atmosphere during the annealing. It is difficult to decompose the relationship formed by diffusion between Al and Li during high-temperature annealing. The most effective method to decompose the relationship is to anneal the as-implanted ZnO at a pressure of 5×10-3 torr. This annealing increases the Al solubility limit because the ZnO surface evaporates.

Abstract: Nanocrystalline and microcrystalline Fe-10Cr alloys were prepared by high energy ball milling followed by compaction and sintering, and then oxidized in air for 52 hours at 400°C. The oxidation resistance of nanocrystalline Fe-10Cr alloy as determined by measuring the weight gain after regular time intervals was compared with that of the microcrystalline alloy of same chemical composition (also prepared by the same processing route and oxidized under identical conditions). Oxidation resistance of nanocrystalline Fe10Cr alloy was found to be in excess of an order of magnitude superior than that of microcrystalline Fe10Cr alloy. The paper also presents results of secondary ion mass spectrometry of oxidized samples of nanocrystalline and microcrystalline Fe-Cr alloys, evidencing the formation of a more protective oxide scale in the nanocrystalline alloy.

Abstract: The behavior of hydrogen in (Ba,Sr)TiO3 (BST) thin film capacitors under electric fields was investigated by performing secondary ion mass spectroscopy (SIMS) analyses. It was clearly observed that the ingress of atmospheric hydrogen into BST thin film capacitors occurred through the anode and that it diffused toward the cathode under electric fields. In addition, it was found that the deterioration of the I-V properties of the BST thin film capacitors can be interpreted in terms of the distribution of hydrogen concentration in the BST thin films.

Abstract: The relationship between the defect structure and luminescence property of ZnO ceramics implanted with Ar of 2×1015 – 60×1015 ions/cm2 was studied. After annealing, the heavy dose-implanted sample (Ar ≥ 30×1015 ions/cm2) was characterized by a luminescence peak at the 730-nm wavelength. Defects in the implanted region formed voids during post-annealing. Oxygen tracer experiments indicated that grain boundary diffusion in the implanted region was enhanced significantly.

Abstract: The relationship between the distribution of hydrogen and the electrical properties of (Ba, Sr)TiO3 (BST) thin film capacitors was investigated using secondary ion mass spectroscopy (SIMS) analyses. It has been clearly shown that there is a close relationship between the hydrogen distribution in BST thin film and the frequency dependence of the complex impedance of the BST thin film capacitors. It was confirmed that protons, the interstitial hydrogen impurity dissolved in BST thin films annealed at 400oC, were produced by a thermal equilibrium reaction between the hydrogen in the annealing atmosphere and the BST thin films.

Abstract: The effect of ion implantation leading to contamination and diffusion of lithium impurity in ZnO ceramics substrates was investigated. The diffusion coefficients of Li in the implanted ZnO annealed at 1000 and 850°C were in good agreement with those in the non-implanted ZnO. At 700°C, Li diffusion in the implanted ZnO was strongly enhanced. Our results show that the defects introduced by the implantation enhance the impurity diffusion at low temperature annealing.