발간논문

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The structural, magnetic and magnetoresistance properties of CoFe/Ag multilayers prepared by magnetron sputter were studied. The uniformity of multilayer was optimized when the multilayer was prepared under 2 mTorr Ar/10%H₂atmosphere and 100 Ｗ input power. Although the structural evolution of discontinuous multilayer was slow, the increase of MR ratio and the structural stability was high when the multilayer was uniform. The MR ratio of CoFe 12 Å/Ag 70 Å multilayer, which was annealed for 20 minutes at 350℃ was 3.8% and the saturation field was 90 Oe.

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Origins for transconductance dispersion and gate leakage current in an AlGaAs/InGaAs pseudomorphic high-electron-mobility transistor (p-HEMT) were found by capacitance deep-level transient spectroscopy(DLTS) measurements. In DLTS spectra, we observed a couple of surface states with thermal activation energies of (0.50±0.03) eV and (0.81±0.01) eV and the DX-center with thermal activation energy of (0.42±0.01) eV. Transconductance was increased in the low frequency range and then decreased in the high frequency range. The transition frequency shifted to higher frequency with the increase of temperature and the activation energy for the change of the transition frequency was determined to be (0.39±0.03) eV. It was found that the activation energy for the conductance of electrons on the surface of p-HEMT was (0.55 ±0.01) eV. Comparing the activation energy of DX-center and surface states with those for transconductance dispersion and gate leakage current, we found DX-centers and surface states H1 caused transconductance dispersion and gate leakage current, respectively.

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Effects of Ar ion damage of Pt bottom electrodes on selective nucleation and growth of PZT thin films have been investigated. As the degree of damage on the Pt bottom electrode increased by increasing the acceleration voltage in the ion mass doping system, PZT thin films on Pt electrode lose their (111) preferred orientation and incubation time for phase transformation from pyrochlore to perovskite structure was increased. 40 ㎛×40 ㎛ square shaped single grain array of PZT thin films could be obtained utilizing the difference of incubation time of damaged and undamaged region of Pt bottom electrodes. Single grained PZT thin films show low leakage current density of 1×10^(-7) Ａ/㎠ and high breakdown field of 440 ㎸/㎝. The loss of remanent polarization after 10^(11) cycles was less than 15% of initial value.

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C54-TiSi₂ grown on SiO₂ as an interconnect showed thermal instability, even skinning, through the rapid thermal anneal(RTA). In order to understand the thermal instability of C54-TiSi₂ the interface between the thin film and the substrate was analyzed with Auger electron spectroscopy(AES) and transmission electron microscopy(TEM). Also we quantitatively analysed residual stress using known thermal properties of C54-TiSi₂. It was noted, as a result, that considerable amounts of residual stress were released by silicon retained at the interface. Therefore surplus silicon should be prepared between titanium and substrate in order to make C54-TiSi₂ thermally stable, so that the surplus silicon may play a role of buffer against residual stress.

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