Metalorganic Decomposition Technique Research Articles

Preparation of Bi4Ti3O12/Bi2SiO5/Si Structures Derived by Metal Organic Decomposition Technique

Bismuth titanate (Bi4Ti3O12) thin films were fabricated on a bismuth silicate (Bi2SiO5)-coated silicon substrate by the metal-organic decomposition (MOD) method. It was confirmed that the resultant films were single-phase Bi4Ti3O12 thin films with c-axis-dominant orientation. However, the fabricated films have a high leakage current density of approximately 104 A·cm-2. It is considered that this is mainly caused by the surface roughness due to the growth of plate-like grains. The growth of the Bi4Ti3O12 thin films using the MOD method is influenced by the substrate. Therefore, it is regarded that the addition of Bi2SiO5 thin film improves the crystallinity of Bi4Ti3O12 thin films.

Fabrication and Characterization of Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) Structures Using Ferroelectric (Bi, La)4Ti3O12 Films

We have fabricated and characterized Pt/(Bi, La)4Ti3O12(BLT)/Pt/Ti/SiO2/Si metal-ferroelectric-metal-insulator-semiconductor (MFMIS) structures for ferroelectric-gate transistor applications. It is demonstrated that BLT films fabricated using the metalorganic decomposition (MOD) technique at 750°C have excellent electrical properties. Remanent polarization 2Pr as large as 30 µC/cm2 can be obtained. It is also shown that in the memory window increases with the area ratio SF:SM of the MFMIS structure and that a large memory window (3 V) can be obtained for a voltage sweep of ±5 V for MFMIS structures with an area ratio SF:SM of 1:15. In addition, it is demonstrated that MFMIS structures with an area ratio SF:SM of 1:15 have good data retention characteristics.

InAs/InAsSbP light-emitting structures grown by gas-phase epitaxy

Using the metal-organic chemical vapor decomposition technique, light-emitting diodes based on InAs/InAsSbP double heterostructures emitting in a wavelength range around 3.3 µm have been fabricated. The external quantum yield of the diodes is 0.7%. In laser diodes, stimulated emission at a wavelength of 3.04 µm has been obtained at T=77 K.

Enhanced fatigue property of PZT thin films using LaNiO3 thin layer as bottom electrode

A highly (100)-oriented metallic LaNiO3 film was prepared directly on a Si substrate by a simple metalorganic decomposition (MOD) technique using lanthanum nitrate and nickel acetate as the starting sources. Subsequent Pb(Zr,Ti)O3 (PZT) thin films deposited on the LaNiO3-coated Si substrate were obtained by a modified sol–gel method. It was found that the PZT thin films began to form a single perovskite phase at a low annealing temperature of 530 °C, and exhibited highly (100) orientation. A ferroelectric capacitor of Pt/Pb(Zr,Ti)O3/LaNiO3/Si annealed at 600 °C displayed a good P-E hysteresis characteristic and was fatigue-free even after 1011 switching cycles.

Abnormal ferroelectric properties of compositionally graded Pb(Zr,Ti)O3 thin films with LaNiO3 bottom electrodes

We report abnormal ferroelectric properties of compositionally graded Pb(Zr,Ti)O3 thin films on LaNiO3-coated SiO2/Si substrates, where Pb(Zr,Ti)O3 and LaNiO3 films were prepared by a metalorganic decomposition technique and a sol–gel technique, respectively. It was found that the hysteresis loops of the Pb(Zr,Ti)O3 graded films measured by the conventional Sawyer–Tower method shifted along the polarization axis, i.e., they showed polarization offsets when applied by an alternating electric field. The polarization offsets were 82.5 μC/cm2 at 270 kV/cm and 62.5 μC/cm2 at 185 kV/cm for the up-graded film and the down-graded film, respectively. The absolute magnitude of the polarization offsets was closely related to the magnitude of the driving electric field, and the direction of the polarization offsets depended on the direction of the composition gradient with respect to the substrate. Analysis indicated that the polarization offsets did not originate from asymmetric contact effects, oxygen vacancies, alignment of defect dipoles, and/or electron injection. These results showed that polarization offsets in hysteresis loops were the intrinsic characteristic of the compositionally graded Pb(Zr,Ti)O3 thin films.

Preparation of highly (1 0 0)-oriented metallic LaNiO 3 films on Si substrates by a modified metalorganic decomposition technique

LaNiO 3 thin films were deposited on Si substrates by a modified metalorganic decomposition technique using lanthanum nitrate and nickel acetate as the start sources. The structures of the films were characterized by X-ray diffraction and scanning electron microscope. Highly (1 0 0)-oriented LaNiO 3 films with smooth and crack-free surfaces were obtained using rapid thermal annealing method. The resistivity versus temperature curves of the textured LaNiO 3 films showed that the films possessed good metallic character.

Lithium niobate thin films on diamond/silicon substrates for surface acoustic wave filter device applications

Piezoelectricity and surface acoustic wave (SAW) propagation of a LiNbO3/diamond/silicon multilayer structure are reported for the first time. Theoretical calculations predict lithium niobate thin films on diamond/silicon substrates have both high SAW propagation velocities and high electromechanical coupling coefficients. The metal-organic decomposition (MOD) technique is used to grow lithium niobate thin films on diamond/silicon substrates. X-ray diffraction analysis shows that the lithium niobate films are polycrystalline. SAW devices are fabricated by depositing interdigital transducers (IDTs) onto the LiNbO3/diamond/silicon films. The SAW activities are observed by measuring the frequency response of the SAW device.

Electrical characteristics of high dielectric constant BCTZ thin films

High dielectric constant Ba0.96Ca0.04Ti0.84Zr0.16O3 (BCTZ) thin films were deposited on Pt/Ti/SiO2/Si substrates by spin on metal-organic decomposition (MOD) technique. Undoped and 0.4% Mg-doped BCTZ thin films were annealed in the temperature range from 600 to 900 °C for 1 hour in oxygen environment. The crystal structure of BCTZ thin films was analyzed by X-ray diffraction. The electrical properties of BCTZ thin films were investigated by capacitance—voltage (C—V) characteristics. Also, the electrical properties of these films were compared in conjunction with 0.4% Mg doping effect of BCTZ thin films for possible high dielectric constant material applications.

Mod preparation and characterization of blt thin film

The bismuth layered perovskite structured ferroelectrics (BLSF) are well known for their good ferroelectric characteristics. Recently, SrBi2Ta2O9 (SBT) and SrBi2Ta2-xNbxO9 (SBTN) have shown attractive properties for ferroelectric random access memories because of their high endurance characteristic. In addition to SBT and SBTN, their lies a possibility of many different BLSF materials waiting to be explored. One such material is lanthanum substituted bismuth titanate Bi4-xLaxTi3O12 (BLT) that has received some attention lately. The BLT thin films were prepared by conventional metal organic decomposition technique on the platinum electrode for evaluating ferroelectric characteristics of BLT and possibility of low temperature crystallization. It was found that BLT can be crystallized at 550C with random orientation and very good ferroelectric properties were observed: the remnant polarization (2Pr) was over 20μC/cm2 with low leakage current. Furthermore, the BLT capacitor did not show any significant fatigue up to 3.2×1010 cycles even at 85C.

Growth of (1 0 0)-oriented LaNiO 3 thin films directly on Si substrates by a simple metalorganic decomposition technique for the highly oriented PZT thin films

LaNiO 3 (LNO) thin films directly on Si (1 0 0) substrates were prepared by a simple metalorganic decomposition (MOD) technique at annealing temperatures ranging from 450°C to 650°C using a rapid thermal annealing (RTA) method. Highly (1 0 0)-oriented LNO thin films were obtained at low annealing temperature of 550°C. The results indicate the LNO film annealed at 600°C exhibits good metallic property, which is comparable with the LNO films derived from physical techniques. A subsequent deposition of sol–gel derived Pb(Zr 0.52Ti 0.48)O 3 (PZT52/48) thin film on the LNO-coated Si substrate was also found to have a (1 0 0)-oriented texture. The ferroelectric capacitor derived from these films displayed a good P– E hysteresis characteristic.

Fabrication of Y123 coated conductors using metal organic decomposition process

Recent trends in HTS research have been geared toward development of coated conductors. In these conductors, a flexible metallic substrate, typically a nickel alloy, is covered successively with one or more thin buffer layer such as YSZ, STO, MgO, etc., and a relatively thick film of Y123. To make the fabrication of such conductors scalable and cost effective, this paper demonstrates the application of metal organic decomposition techniques to deposit the buffer layers and the YBCO films. We present results obtained strontium titanate buffer layers. These buffer layers, processed on single crystal substrates using solution precursors and heat treated in a reducing atmosphere are highly textured and have a uniform smooth surface. YBCO films, 0.3–0.5μm thick, deposited on these buffered single crystals using the trifluoroacetate process shows good superconducting properties. YBCO films processed on strontium titanate buffered lanthanum aluminate substrates have transition temperatures of 90–91 K and critical current densities of the order of 10 5 A/cm 2 at 77K and self field. These processing techniques have been extended to textured nickel substrates. These results offer promise to the development of a scalable, solution based processing route to deposit buffer layers and YBCO films on flexible metallic textured tapes.

Laser annealing of SrBi 2Ta 2O 9 thin films

A laser annealing technique was used to fabricate SrBi 2Ta 2O 9 (SBT) thin films at a low temperature. Amorphous SBT thin films were prepared on Pt/Ti/SiO 2/Si substrates by a metalorganic decomposition (MOD) technique. A two-step process was used to crystallize the amorphous thin films: the films were annealed at 550°C for 0.5 h to initiate the nucleation of the SBT phase, and then annealed with a KrF excimer laser. X-Ray diffraction (XRD) patterns showed that the laser-annealed thin films were transformed into a SBT perovskite structure without the presence of a second phase. The films irradiated by laser with a lower energy density and a greater pulse number had a better grain and a rougher surface.

Preparation and electric properties of SrBi 2Ta 2O 9 thin films by MOD method

Polycrystalline SrBi 2Ta 2O 9 (SBT) ferroelectric thin films were prepared on Pt/Ti/SiO 2/Si substrates by the metalorganic decomposition (MOD) technique. The dielectric properties of SrBi 2Ta 2O 9 (SBT) capacitors were measured with HP4194 and RT6000HVS testers. The experimental results exhibited that the dielectric constant ε r ( f) and ac conductivity σ( f) of SBT thin films had a power law dependence on frequency. An increase in the ac conductivity with increasing frequency showed the relaxation of the leakage current of the SBT capacitors in the first stage. The dielectric constant and ac conductivity were dependent on the thickness, temperature, grain size, and annealing ambient, etc. of the SBT thin films.

Structural and electrical properties of PbTiO 3 thin films on conductive oxide LaNiO 3 coated Si substrates prepared by sol–gel method

Conductive LaNiO 3 (LNO) thin films were grown on Si substrates by metalorganic decomposition (MOD) and their application as the bottom electrodes for the growth of sol–gel derived PbTiO 3 (PT) thin films. The structure, morphology and electrical properties of the multilayer films were characterized by some analytical techniques and electrical measurements. PT film on LNO/Si had pure perovskite phase with sharp cross-section and small surface roughness. Most Raman modes of PT films shifted to the low frequency due to the pressure effect in the films. PT capacitor showed saturated hysteresis loop, higher resistivity and breakdown voltage. These results indicated the PT/LNO/Si heterostructure fabricated by sol–gel and MOD techniques to be a promising combination for microelectronic device.

Effects of processing on the characteristics of SrBi2Ta2O9 films prepared by metalorganic decomposition

SrBi 2 Ta 2 O 9 (SBT) films were prepared by metalorganic decomposition technique. The films were obtained by spin-on pyrolysis of the precursor solutions on various substrates and then annealed at 550–850 °C in dry oxygen, wet oxygen, or Ar. Effects of precursor solution concentration, anneal temperature, anneal atmosphere, substrate and Ar ion sputtering on the microstructure, morphology and electrical properties were investigated by means of x-ray diffraction, scanning electron microscope, atomic force microscope, x-ray photoelectron spectroscopy, and electrical measurements. The results indicated the grain size, and the remnant polarization (Pr) increased with increasing the anneal temperature up to 800 °C and the significant hysteresis loop could be obtained only after anneal above 700 °C. At 850 °C, the pyrochlore phase and other secondary phases were observed along with the SBT phase, leading to the decreasing Pr and dielectric constant. In addition, the development of crystalline phase and electrical properties were affected by anneal atmosphere. When annealed in Ar at 750 °C, the layered SBT structure was destroyed with evident Bi loss. As though the original structure could be restored basically by subsequent adequate O2 anneal, the electrical properties were deteriorated seriously due to the shorted capacitor. Wet oxygen anneal evidently deformed the morphology and the hysteresis loop. This was attributed to the effect of possible produced slight H2 due to the reaction between H2O and residual carbonaceous in films under Pt catalyst. Substrates also played an important role on film crystallinity. The films deposited on Si, SrTiO3, and crystal quartz at 750 °C had a layered perovskite polycrystalline structure while the films on fused quartz exhibited poor crystalline nature even after 800 °C anneal and films on NaCl showed (200)-predominant orientation of SBT phase with some pyrochlore. In addition, Ar ion sputtering might lead to the severe Bi and oxygen deficiency in the surface of the sputtered film.

BiVO 4 thin film preparation by metalorganic decomposition

This paper describes the first obtention of BiVO 4 thin films. These films were prepared with the Metalorganic Decomposition technique, starting from bismuth 2-ethyl-hexanoate and vanadium (IV) (oxy)acetylacetonate precursors. These compounds were dissolved in freshly distilled acetylacetone, dip-coated on common borosilicate glass substrates and pyrolysed at 400°C. Film thickness ranged from 50 to 100 nm, depending on the number of deposition steps. Films are transparent, allowing the first obtention of UV–vis absorption spectra acquisition in transmission mode. Raman microprobe spectra confirmed the obtention of BiVO 4 deposited as an homogeneous film. Scanning electron micrographs showed a continuous and porous surface.

Low-temperature preparation and characterization of SrBi2Ta2O9 thin films on (100)-oriented LaNiO3 electrodes

SrBi 2 Ta 2 O 9 (SBT) ferroelectric thin films were prepared by the metalorganic decomposition technique at annealing temperatures of 600 and 650 °C on Pt/Ti/SiO2/Si substrates coated by (100)-oriented LaNiO3 (LNO) metal oxide thin films, which were fabricated by the sol–gel technique combined with a layer-by-layer annealing method at 600 °C. A (200)-predominant SBT thin film can be formed on LaNiO3(100)/Pt/Ti/SiO2/Si substrate at 600 °C. The effect of the LNO oxide electrode on the dielectric and ferroelectric properties of SBT thin film annealed at 600 °C was studied. Although the remanent polarization of the (200)-predominant SBT thin film is not as large as expected, the film can be uniformly polarized and imaged using an atomic force microscope in the piezoelectric mode.

Application of metal–organic decomposition techniques for the deposition of buffer layers and Y123 for coated-conductor fabrication

Recent developments in the fabrication of long length textured substrates have increased the focus on YBCO-based tapes for application as long-length conductors. A typical coated conductor consists of a metal substrate coated with a buffer layer on which YBCO is deposited in the form of a thick film. To make the fabrication of such conductors scalable and cost effective, this paper explores the possibility of applying metal–organic decomposition (MOD) techniques to deposit the buffer layers and the YBCO films. Two possible buffer layer candidates have been studied, namely, barium zirconate and strontium titanate. These buffer layers have been processed on single crystal substrates using solution precursors and heat treated in a reducing atmosphere, which makes the deposition techniques metal friendly. It has been found that these buffer layer films processed on single-crystal substrates are highly textured and have a uniform smooth surface. YBCO films, 0.3–0.5 μm thick, deposited on these buffered single crystals using the trifluoroacetate process, show good superconducting properties. YBCO films processed on barium zirconate buffered strontium titanate have transition temperatures of 86–88 K and critical current density of the order of 10 4 A/cm 2 at 77 K and self-field. YBCO films processed on strontium titanate-buffered lanthanum aluminate substrates have transition temperatures of 90–91 K and critical current densities of the order of 10 5 A/cm 2 at 77 K and self-field. These results offer promise to the development of a scalable, solution-based processing route to deposit buffer layers and YBCO films on flexible metallic textured tapes.

The Effect of Annealing Temperature on Electrical Properties of SrBi2Ta2O9/Insulators/Si(MFIS) Structure for NDRO-type FRAM Devices

We have fabricated Pt/SBT/insulator/Si structure for the transistor gate in MFIS-FET and investigated the electrical properties of MFIS structure with various insulator materials. SrBi 2 Ta 2 O 9 films as a ferroelectric layer were deposited by metal organic decomposition (MOD) technique, on various insulator structures including SiON, and Al 2 O 3 as well as on Pt/Ti/SiO 2 /Si structures. The effect of annealing temperature on the electrical properties of MFIS structures was investigated in order to analyze the applicability to conventional CMOS process. Although the remnant polarization of SBT films for MFM structure was increased with increasing annealing temperature, the memory window which has a relationship with remnant polarization of ferroelectrics was differently displayed with insulator structure in MFIS structure.

Graded PZT thin film capacitors with stoichimetric variation by MOD technique

By tailoring Zr/Ti ratio in Pb(Zr,Ti)O3 from 45/55 to 75/25, functionally graded PZT thin films were prepared by metal organic decomposition (MOD) technique. P-E hysteresis loops were measured, and polarization was found to shift up or down depending on the direction of the composition gradients of the PZT. This polarization offset was modeled using Poisson's equation in one dimension. Switching charge was also found to be compositional gradient direction dependent.