Meng-Shian Lin

Process study of chemically vapour-deposited SnOx (x≈2) films

Abstract The physical characteristics of SnOx(x≈2) films deposited onto Pyrex glass substrates by chemical vapour deposition are studied. The temperature dependence indicates that films deposited at 600 °C have good polycrystallinity. The electrical conductivity of the 600 °C films is mainly controlled by the variation in the SnCl4 vapour flow rate. A subsequent thermal annealing process can even reduce the sheet resistance to 400ω/□. In addition, the visible absorption shows that the 600 °C films tend to lose their transparency in the short wavelength range of the visible spectrum.

Perpendicular interlayer coupling through oscillatory Ruderman-Kittel-Kasuya-Yosida interaction between Co∕Pt multilayers and Co∕TbCo bilayers

The oscillatory perpendicular interlayer-coupling field and strength as a function of Ru spacer thickness were studied for samples of the [Co∕Pt]5∕Co∕Ru∕Co∕TbCo structure. For Ru thickness in the range of 0.5–1nm, a strong antiferromagnetic (AF) coupling (J∼0.38erg∕cm2) was observed. When AF coupling existed, the coercivity of Co∕TbCo bilayers was enhanced because the Co∕Pt multilayers stabilized the magnetization direction of Co∕TbCo. Consequently, oscillatory coercivity of Co∕TbCo with Ru thickness was also observed. Since the magnetization direction of the Co sublattice in TbCo can be tuned by adjusting composition or measuring temperature, the direction of the shifted minor loop of Co∕Pt multilayers can be varied accordingly while keeping the same Ru thickness.

Influence of NH3 plasma pretreatment on the properties of plasma enhanced chemical vapor deposited SiON on GaAs interface

Interface properties of plasma‐enhanced chemical‐vapor‐deposited dielectric SiON on GaAs systems pretreated by NH3 plasma were studied. The effects of the process parameters in the NH3 plasma pretreatment, such as total pressure, radio‐frequency power, substrate temperature, NH3 flow rate and pretreatment time, were investigated by the measurements of Auger electron spectroscopy, Raman spectroscopy, current‐voltage, and capacitance‐voltage characteristics. The transient region width and the surface strain field, surface leakage current, hysteresis, and degree of Fermi‐level pinning evidently related to interface properties, are increased with increasing total pressure, decreased with increasing radio‐frequency power, substrate temperature, and pretreatment time, and independent of NH3 flow rate. The physical and electrical properties of SiON/GaAs interface have been significantly improved under an optimum NH3 plasma pretreatment condition. The correlation of these parameters in pretreatment process with t...

Thermal annealing study on GaAs encapsulated by plasma‐enhanced chemical‐vapor‐deposited SiOxNy

To avoid the thermal decomposition of the GaAs surface during the postimplanted annealing, a silicon oxynitride (SiOxNy) encapsulate layer grown by plasma‐enhanced chemical vapor deposition has been systematically studied. SiOxNy with the refraction index of 1.7–1.8 exhibited the best encapsulated performance after high‐temperature annealing. Using Raman spectroscopy, etch‐pit densities, photoluminescence, and Hall‐effect measurements, this composition of the encapsulate layer on GaAs possessed the lowest surface defect, the best thermal stability, and the highest electrical activity of the implanted dopant. Thermal conversion is present when SiO‐ and SiN‐ rich films are used and is tentatively attributed to the generation of Ga vacancies during the annealing process.

Perpendicular giant magnetoresistance composed of [Co∕Pt] multilayer and CoFe∕TbCo

Perpendicular spin valves composed of [Co∕Pt] multilayer and CoFe∕TbCo bilayer were fabricated. The perpendicular giant magnetoresistance ratio of 4.8% was obtained with current-in-plane measurements. The interlayer coupling increased with increasing the net magnetization of CoFe∕TbCo. We proposed a perpendicular pinning structure which possessed a high perpendicular coercivity (7000 Oe) but zero net moment. Consequently, the interlayer coupling between free and pinned layers can be significantly suppressed. This perpendicular pinning structure can be potentially used for high-density perpendicular magnetic random access memory cells.

Effects of laminated soft layer on magnetization reversal of exchange coupled composite media

The laminated soft layer (LSL) that comprises the granular [CoPtCr–SiO2/Pt]N multilayers with perpendicular magnetization is designed to reduce the switching field of exchange coupled composite (ECC) media. The magnetic simulation shows that the reduction in the switching field can be optimized by changing the coupling strength between the adjacent CoPtCr–SiO2 layers in LSL. The reversal mechanism of ECC media with LSL depends on the bilayers number N of [CoPtCr–SiO2/Pt]N. Both simulation and experiments reveal that the domain-wall assisting reversal strongly depends on the thickness of LSL. By properly adjusting the coupling strength inside the LSL, the switching and saturation fields can be significantly reduced at a limited thickness of the soft layer due to decreased domain-wall length by the Pt lamination.

Direct probing magnetization reversal of exchange-coupled-composite media by x-ray magnetic circular dichroism

X-ray magnetic circular dichroism (XMCD) was used to directly probe the depth-dependent magnetization reversal of CoPtCr-SiO2-based exchange-coupled-composite media with laminated soft layers. A thin Fe-marker layer in the soft layer was used as the indicator of local magnetization. Element-specific XMCD loops of Fe-marker layers confirmed the transition of the magnetization reversal from rigid magnets to exchange-spring magnets with increasing thickness of the soft layer. The micromagnetic simulations revealed the importance of the reduced exchange constant (Asoft) by laminating the soft layer for domain-wall assisting reversal. By comparing XMCD loops with simulations, we can deduce the effective Asoft.

Transmission electron microscope study of ion beam annealing effects of ion‐implanted and evaporated amorphous silicon

High power ion beam annealing has been applied to ion‐implanted and evaporated amorphous silicon samples. Microstructures induced by this novel technique have been investigated by transmission electron microscope. The analysis of diffraction patterns and direct images of ion beam annealed as well as thermally annealed specimens indicates that ion beam annealing is a promising technique to process ion‐implanted and evaporated amorphous samples. It was found that several seconds of intense ion beam bombardment produced similar effects as did 1‐h 600–900 °C thermal annealing.

Optimization of exchange coupled composite media by tuning the anisotropy in a laminated soft layer

The laminated soft layer (LSL) [Pt/CoPtCr-SiO2]5 was used in exchange coupled composite (ECC) media and exhibited a tunable perpendicular anisotropy by changing the thickness of Pt. By using x-ray magnetic circular dichroism, the incoherent reversal in the ECC media with a LSL was directly observed. The nucleation field of ECC media was found to be dominated by the anisotropy of the LSL. The increased thickness of the Pt layers in the LSL reduced the anisotropy, which promoted incoherent reversal; however, with the Pt thickness increasing larger than 0.9 nm, the interlayer coupling between the LSL and the hard layer was significantly reduced, and thus the assisting effect was suppressed. Furthermore, the dependence of remanent coercivity Hcr on the Pt thickness confirmed that the assisting effect can be optimized by controlling the Pt thickness to balance the LSL anisotropy and the interlayer coupling.

Interface properties of plasma‐enhanced chemical vapor deposited SiOxNy/n‐GaAs metal‐insulator‐semiconductor system

Interface properties of plasma‐enhanced chemical vapor deposited SiOxNy/n‐GaAs metal‐insulator‐semiconductor systems are investigated by capacitance‐voltage and deep level transient spectroscopy measurements. At room temperature, these metal‐insulator‐semiconductor devices exhibit deep depletion mode operation which is characteristic of the low thermal generation rate for minority carriers in GaAs and the large number of traps located at or near the interface. For accumulation mode bias voltage, the small signal capacitance does not approach the SiOxNy capacitance and exhibits anomalous frequency dispersion behavior. A simple method is used to correlate the capacitance‐voltage and deep level transient spectroscopy data. An interface‐state band model best fits the experimental results.