Formation of Zr-contained Amorphous Alloy Films by Magnetron Co-sputtering

In order to explore the application of magnetron co-sputtering in fabricating the amorphous alloy, Zr-contained amorphous films were prepared by this technique and investigated by scanning electron microscope, energy disperse spectroscopy and X-ray diffraction. The results show that the co-sputtered films are in fully amorphous state or with amorphous-nanocrystal 1 ine structure. The XRD patterns of the Zr-Cu and Zr-Ni amorphous films exhibit a double-peak phenomenon. There is a shift of diffusive peak with changing the sputtering current which is possibly attributed to the change of Zr-Ni and Zr-Cu intermetallic like short range orders. In addition, Zr-Cu-Ni ternary co-sputtered films have a sharper peak at high angle. The sputtering yield of element during co-sputtering ranks as Cu>Ni>Zr, which can be ascribed to the contribution of melting and boiling temperature, atomic size and electrical conductivity of elements.

Structural,optical,and electrical properties of Cu-doped ZrO_2 films prepared by magnetron co-sputtering

Copper （Cu）-doped ZrO2 （CZO） films with different Cu content （0 at.%- 8.07 at.%） are successfully deposited on Si （100） substrates by direct current （DC） and radio frequency （RF） magnetron co-sputtering. The influences of Cu content on structural, morphological, optical and electrical properties of CZO films are discussed in detail. The CZO films exhibit ZrO2 monocline （1^-11） preferred orientation, which indicates that Cu atoms are doped in ZrO2 host lattice. The crystallite size estimated form x-ray diffraction （XRD） increases by Cu doping, which accords with the result observed from the scanning electron microscope （SEM）. The electrical resistivity decreases from 2.63 Ω·cm to 1.48 Ω·cm with Cu doping content increasing, which indicates that the conductivity of CZO film is improved. However, the visible light transmittances decrease slightly by Cu doping and the optical band gap values decrease from 4.64 eV to 4.48 eV for CZO fihns.

Structural,Morphological and Electrical Properties of In-Doped Zinc Oxide Nanostructure Thin Films Grown on p-Type Gallium Nitride by Simultaneous Radio-Frequency Direct-Current Magnetron Co-Sputtering

Zinc oxide （ZnO） is one of the most promising and frequently used semiconductor materials. In-doped nanos- tructure ZnO thin films are grown on p-type gallium nitride substrates by employing the simultaneous rf and dc magnetron co-sputtering technique. The effect of In-doping on structural, morphological and electrical properties is studied. The different dopant concentrations are accomplished by varying the direct current power of the In target while keeping the fixed radio frequency power of the ZnO target through the co-sputtering deposition technique by using argon as the sputtering gas at ambient temperature. The structural analysis confirms that all the grown thin films preferentially orientate along the c-axis with the wurtzite hexagonal crystal structure without having any kind of In oxide phases. The presenting Zn, 0 and In elements＇ chemical compositions are identified with EDX mapping analysis of the deposited thin films and the calculated M ratio has been found to decrease with the increasing In power. The surface topographies of the grown thin films are examined with the atomic force microscope technique. The obtained results reveal that the grown film roughness increases with the In power. The Hall measurements ascertain that all the grown films have n-type conductivity and also the other electrical parameters such as resistivity,mobility and carrier concentration are analyzed.

Effects of Vanadium Content on Structure and Chemical State of TiVN Films Prepared by Reactive DC Magnetron Co-Sputtering

TiVN films were deposited on Si(100) wafers without external heating and biasing by reactive dc magnetron co-sputtering. Titanium and vanadium metals were used as sputtering targets. Ar and N2 gases were used as sputtering gas and reactive gas, respectively. The flow rates of Ar and N2 were 8 and 4 sccm, respectively. The Ti sputtering current (ITi) was kept constant at 0.6 Aand V sputtering current (IV) was varied from 0.4 to1.0 A. The deposition time for all the deposited films was 30 min. The effects of V sputtering current on the structure, surface and cross-sectional morphologies, and chemical composition and chemical state of the films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. It was found that all the prepared film formed (Ti,V)N solid solution. The lattice parameter was found to decrease while crystallite size, RMS roughness and film thickness increased with increasing V sputtering current. High resolution XPS spectra of the Ti 2p, V 2p and N 1s revealed that the fraction of Ti-N and V-N bonds increased as the V sputtering current increased. However, the V-N bond was observed only at a high V sputtering current.

Structure and optical characterization of GaP-SiO_2 co-sputtered films

The films of GaP nanocrystals embedded in SiO2 matrix were prepared by radio frequency magnetron co-sputtering and subsequent annealing technology. The structure and morphology of the films were investigated by scanning electron microscope, X-ray diffraction, and energy dispersive spectrum. Raman spectra results showed that the transverse optical phonon model （TO） and the longitudinal optical phonon model （LO） of GaP nanocrystals were both discovered to undergo red shift, broadening, and asymmetry. The red shift degree of the TO model was about 8.8 cm^-1. The luminescence spectrum of the GaP/SiO2 film consisted of several emission peaks. 2.84-2.54 eV blue light emission was explained by the quantum confinement-luminescence centers model （QC-LCs）.

Magnetron co-sputtering synthesis and nanoindentation studies of nanocrystalline(TiZrHf)_(x)(NbTa)_(1–x)high-entropy alloy thin films

Refractory high-entropy alloys(HEAs)possess many useful properties such as high strength and high-temperature stability.So far,most studies on refractory HEAs have been limited to a few well-known compositions and on their coarse-grain bulk forms.Here we fabricate nanocrystalline(TiZrHf)_(x)(NbTa)_(1−x)HEA thin films with a large range of compositions(x=0.07–0.90)by the direct current(DC)magnetron co-sputtering technique and measure their mechanical properties using the nanoindentation method.All the as-deposited HEA thin films show a solid-solution body-centered cubic(bcc)structure.As the compositional ratio(x)increases,the elastic modulus decreases from 153 to 123 GPa,following the trend of the rule of mixture.As x increases,the hardness first decreases from 6.5 GPa(x=0.07)to the lowest value(4.6 GPa,x=0.48)and then increases to the highest value(7.1 GPa,x=0.90),showing a concave trend.The change in hardness might be attributed to the combinational influence caused by the atomic size and modulus effects,as well as the texture effect.The authors also propose a few open questions for future studies on this and related HEA systems.

A combinatorial approach of developing alloy thin films using co-sputtering technique for displays

In this study we have used a combinatorial approach for producing binary and ternary alloy thin film libraries using a lab-scale RF co-sputtering system. Initially we used two elemental sputtering targets, i.e. aluminum (Al) target and neodymium (Nd) target, to produce a film library of varying composition and successfully identified a suitable composition range (1.95―2.38 at% Nd) in which resistance to hillock formation and resistivity of the film spots were found to be satisfactory in annealed state (350℃, 30 min). In another case, in order to form ternary alloy composition library we have used two sputtering targets, i.e. an Al-0.5 at% Nd alloy target and an elemental Ni target. Though, co-sputtered Al-0.6 at% Nd-0.9 at% Ni alloy films showed satisfactory resistance to hillock formation and low resistivity after annealing, film deposited from a ternary alloy target with the same composition failed to show satis- factory resistance to hillock formation during annealing. In case of Al-0.6 at% Nd-0.9 at% Ni alloy target, 250 nm thick film showed poor resistance to hillock formation than the 500 nm thick film. This clearly showed thickness-dependent hillock performance of Al-0.6 at% Nd-0.9 at% Ni alloy. In this study it was found that, in addition to the process variables, metallurgical microstructure of the alloy sputtering targets had significant effect on the film properties which was not obvious from the results of films deposited using co-sputtering of the individual elemental targets.

Study of Ge_2Sb_2Te_5 Film for Nonvolatile Memory Medium

The amorphous Ge2Sb2Te5 film with stoichiometric compositions was deposited by co-sputtering of separate Ge, Sb, and Te targets on SiO2/Si (100) wafer in ultrahigh vacuum magnetron sputtering apparatus. The crystallization behavior of amorphous Ge2Sb2Te5 film was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and differential scanning calorimetry (DSC). With an increase of annealing temperature, the amorphous Ge2Sb2Te5 film undergoes a two-step crystallization process that it first crystallizes in face-centered-cubic (fcc) crystal structure and finally fcc structure changes to hexagonal (hex) structure. Activation energy values of 3.636±0.137 and 1.579±0.005 eV correspond to the crystallization and structural transformation processes, respectively. From annealing temperature dependence of the film resistivity, it is determined that the first steep decrease of the resistivity corresponds to crystallization while the second one is primarily caused by structural transformation from 'fcc' to 'hex' and growth of the crystal grains. Current-voltage (Ⅰ-Ⅴ) characteristics of the device with 40 nm-thick Ge2Sb2Te5 film show that the Ge2Sb2Te5 film with nanometer order thickness is still applicable for memory medium of nonvolatile phase change memory.

Structure,optical and electrical properties of Nb-doped ZnO transparent conductive thin films prepared by co-sputtering method

Nb-doped ZnO thin films were fabricated on glass substrates by using co-sputtering with direct-current and radio frequency magnetron sputtering.The structures,optical and electrical performances of Nb-doped ZnO thin films were investigated.The results showed that all thin films have(002)c-axis preferential orientation.The minimum resistivity of 2.12×10^(-3)Ωcm and the maximum carrier concentration of 2.39×10^(19 )cm^(-3) were obtained at the direct-current sputtering power of 10W,respectively.Nb-doped ZnO thin films have also shown high average transmittance of 89.6%,and lower surface roughness of 2.74 nm.Meanwhile,a distinct absorption edge in the ultraviolet range of 300–400 nm was observed in absorbance,the optical band gap of Nb-doped ZnO thin films illustrates an increased tendency with increasing Nb concentration.

Tuning magnetic properties, thermal stability and microstructure of NdFeB magnets with diffusing Pr-Zn films

Grain boundary diffusion process(GBDP)serves as a promising approach in improving magnetic properties and thermal stability of Nd FeB permanent magnets.Herein,non-heavy rare earth Pr-Zn films deposited on the magnet surface using DC-magnetron sputtering system are reported.The thermal stability and coercivity enhancement mechanism of Pr-Zn GBDP magnets were investigated.Results show that the coercivity of Pr-Zn GBDP magnet increases from 963.96 kA m^-1 to 1317.14 kA m^-1 without any remanence reduction.Notably,the demagnetization curve of Pr-Zn GBDP magnet still remains a high squareness ratio.The temperature coefficient of coercivity and anti-demagnetization ability of Pr-Zn GBDP magnet under high temperatures are improved after GBDP treatment.The well-optimized rare earth-rich(RE-rich)grain boundary phases and high effective anisotropy field of(Nd,RE)2 Fe14 B magnetic hardening layers surrounding main grains are the key factors to impact the magnetic properties and thermal stability of Nd FeB permanent magnets via GBDP treatment.

Dielectric properties of amorphous Bi-Ti-O thin films

We report the unexpectedly excellent dielectric properties of amorphous thin films with compositions in the Bi-Ti-O system.Films were deposited by RF magnetron reactive co-sputtering.In the composition range of 0.5<x<0.7,amorphous Bi_(1−x)Ti_(x)O_(y) exhibits excellent dielectric properties,with a high dielectric constant,ε_(r)~53,and a dissipation factor as low as tanδ=0.007.The corresponding maximum breakdown field reaches~1.6 MV/cm,yielding a maximum stored charge per unit area of up to 8μC/cm^(2).This work demonstrates the potential of amorphous Bi-Ti-O as a high-performance thin-film dielectric material that is compatible with high-performance integrated circuits.

Atomic-layer-deposited （ALD） Al2O3passivation dependent interface chemistry, band alignment and electrical properties of HfYO/Si gate stacks

In this work, the effects of atomic-layer-deposited(ALD) Al2O3 passivation layers with different thicknesses on the interface chemistry and electrical properties of sputtering-derived HfYO gate dielectrics on Si substrates have been investigated. The results of electrical measurements and X-ray photoelectron sepectroscopy(XPS) showed that 1-nm-thick Al2O3 passivation layer is optimized to obtain excellent electrical and interfacial properties for HfYO/Si gate stack. Then, the metal-oxide-semiconductor capacitors with HfYO/1-nm Al2O3/Si/Al gate stack were fabricated and annealed at different temperatures in forming gas(95% N2+5% H2). Capacitance-voltage(C-V) and current density-voltage(J-V) characteristics showed that the 250℃-annealed HYO high-k gate dielectric thin film demonstrated the lowest border trapped oxide charge density(-3.3 × 1010 cm-2), smallest gate-leakage current(2.45 × 10-6 A/cm2 at 2 V)compared with other samples. Moreover, the annealing temperature dependent leakage current conduction mechanism for Al/HfYO/Al2O3/Si/Al MOS capacitor has been investigated systematically. Detailed electrical measurements reveal that Poole-Frenkle emission is the main dominant emission in the region of low and medium electric fields while direct tunneling is dominant conduction mechanism at high electric fields.