Chang-Man Park

Electrical properties of thin film zirconia grown by ultraviolet ozone oxidation

Zirconia films of varying thickness (ranging from 20–55 A) have been grown by the method of UV ozone oxidation at room temperature. The electrical properties of these films have been studied in detail by capacitance–voltage (C–V) and I–V measurements. Capacitors were subjected to various anneals in differing ambient to study their effects on C–V hysteresis, dispersion and charge trapping. It was found that annealing in nitrogen followed by forming gas resulted in C–V curves with negligible hysteresis. The effects of different underlayers on the electrical properties of zirconia films have also been studied and are briefly discussed. It was found that zirconia films grown on UV-ozone grown SiO2 had lower hysteresis and lower interface trap density compared to zirconia films grown on chemical oxide. The effect of oxidation time and oxygen pressure have been investigated; in particular, detailed electrical studies have been performed on partially oxidized zirconia. Defective oxides are shown to have signific...

Growth and characterization of ultrathin zirconia dielectrics grown by ultraviolet ozone oxidation

In this letter, we report on the growth of ultrathin films of zirconia on silicon oxide and silicon oxynitride passivated (001) Si by ultraviolet ozone oxidation of Zr metal precursor layers. The oxidation kinetics has been measured using an accelerator-based nuclear reaction analysis. It was found that oxide films up to 55 A could be grown at room temperature by oxidation at 600 Torr while oxidation at 80 mTorr is self-limiting at 20 A. The interfaces between the dielectric and the substrate have been characterized by scanning transmission electron microscopy. The ZrO2 films were found to be crystalline as grown. Electrical measurements on capacitor structures with 30-A-thick ZrO2 films grown on native oxide on silicon show a capacitance–voltage hysteresis of 15 mV and a capacitance-based equivalent oxide thickness of 17 A at 100 kHz.

Interface structure and perpendicular magnetic anisotropy in Pt/Co multilayers

Pt/Co multilayers sputter‐deposited in Ar and Xe ambients, and periodic multilayers composed of specific combinations of Pt, Pd, and Co layers, were grown to study the effects of energetic backscattered Ar neutrals on the interface structure. The effects were correlated with the magnetic and magneto‐optical properties with emphasis on the perpendicular magnetic anisotropy, K⊥. Films were characterized by high‐resolution transmission electron microscopy, x‐ray diffraction including grazing incidence geometry, and magnetic circular x‐ray dichroism techniques as well as by standard magnetic and magneto‐optic methods. It is found that the perpendicular magnetic anisotropy is extremely sensitive to the degree of intermixing, sharp interfaces yielding the largest anisotropy. The three to fourfold difference in K⊥ found between Ar and Xe sputtered films can be directly correlated to the magnitude of the orbital moment contribution 〈LZ〉 in the Co. This orbital contribution is found to be strongly sensitive to the...

Enhancement of giant magnetoresistance properties of NiO spin valves with an oxidized free layer naturally in the air

The effect of specular electron scattering on the natural oxidation of a free layer in NiO spin valves has been investigated. The magnetoresistance ratio and the exchange biasing field (Hex) of NiO(600 A)/Ni81Fe19(50 A)/Co(7 A)/Cu(20 A)/Ni81Fe19(70 A) spin valves were increased from 4.9% to 7.3%, and 110 to 170 Oe after the natural oxidation in the atmosphere for 80 days, respectively. The sheet resistance ρ decreased from 28 to 17 μΩ m, but Δρ did almost not change after the oxidation. The spin valves enhanced by the specular electron scattering in the naturally oxidized Co/NiFe/NiFeOx free layer were confirmed from the depth profiles using Auger electron spectroscopy.

Dependence of Natural Oxidation Spin-Dependent Tunneling Junction on Junction Area

The top-type tunneling magnetoresistance (TMR) multilayer films with a structure of Ta5/NiFelO/ Ta5/NiFe10/FeMn10/NiFe2,/CoFe2/Al 2 O 3 1/CoFe3/NiFe20 (thickness in nm) with in-situ natural AlO x oxidation were deposited by a sputtering system with a base pressure of 10 -9 Torr. Junctions with sizes from 4 to 80 μm 2 were fabricated by using a conventional photolithography process. The as-deposited junction showed TMR of 16% at room temperature with resistance of 14-15 Ω, dependent on junction area.

Magnetoresistance in La/sub 0.8/Sr/sub 0.2/MnO/sub 3-/spl delta// biepitaxial grain boundary junction

La/sub 0.8/Sr/sub 0.2/MnO/sub 3-/spl delta// (LSMO) films with 45/spl deg/ in-plane grain boundaries were fabricated using two types of biepitaxial multilayers. The low field MR (magnetoresistance) ratio of 32% at 77 K is a significant value due to the artificial grain boundary effect and it maybe useful for developing spin-dependent tunneling junctions using a LSMO biepitaxial grain boundary. The magnetoresistive properties at two different magnetic fields, parallel or perpendicular to the grain boundary junction, can be interpreted by the different ferromagnetic spin-polarization ordering in ab-plane.

Magnetoresistance in hybrid type YBCO-NiO/NiFe/Cu/NiFe film structure

The magnetoresistance properties of NiO/NiFe/Cu/NiFe spin valve film deposited on MgO(100) substrate with YBa₂Cu₃O_7(YBCO) film were investigated at room temperature and at 77 K. The magnetoresistance (MR) curves of the hybrid superconductor-magnetoresistor film structure showed an exchange coupling field of 300 Oe and an inverse magnetoresistance ratio of -6.5%. The magnetization configurations of the two magnetic layers in the NiO spin valve were antiparallel due to an increment in the conduction electron flow to superconductor YBCO film. This sample showed an inverse MR ratio.

Basic magnetic properties of Nd based permanent magnet Nd/sub 2/Fe/sub 12.7/Cr/sub 1.3/B by bipolar pulse-type hysteresis loop tracer

Introduction The user-friendly and economical bipolar pulsetype hysteresis loop tracers which are able to measure four quadrant 1-H loop of Nd based hi.& coercivity magnet with a single expnimental run were constmucted in our laboratory[l]-[2]. In the later one of two loop hacers. an alternative pulse magnetic field with peak value of about 10 T is generated by a way of c o r n l i n g 3 monopolar pulse generators to an air solenoid magnet by using a sequential ignition circuit aod a magnet exciting circuit in room tempeatore. In this work, using the Imp tracer, basic magnetic properties such as the major and minor I-H Imps with initial magnetization curves, magnetic anisahopy and anisotropic field of rad type Nd based magnet N d r F e t K n J with length of 5 mm and diameter of 3.6 mm, are investigated.