Metalorganic Decomposition Technique Research Articles

IMPRINT RELATED FATIGUE BEHAVIOR OF Pt/SrBi2Ta2O9/Pt CAPACITORS

ABSTRACT Pt/SrBi2Ta2O9(SBT)/Pt ferroelectric capacitors with the film thickness of 300 nm were successfully fabricated using metalorganic decomposition (MOD) technique. The fatigue and imprint behaviors were studied. It is found that the switchable polarization of SBT capacitors had the increasing trend in the first stage, and after 2× 109 switching cycles, the switchable polarization began to decrease. The domains in SBT thin films were weakly pinned by defect charges and they were easily depinned when applying an external field, which resulted in the increase of switchable polarization. Furthermore, the depinned defect charges moved to the electrode interfaces and aggregated there, then resulted in the polarization suppression at last. During the switching process, both the behavior of fatigue and imprint existed simultaneously. A competition relationship existed between the depinning behavior of domains and the aggregation of defect charges at the electrode interfaces. It was the competition that decided the fatigue characterization for SBT capacitors. The higher the external voltage, the more suppressed polarization could be recovered, which suggested that more domains in SBT thin films were easily depinned under a higher external field, and the pinning depth by defect charges was different.

Structural and ferroelectric properties of La modified Sr 0.8Bi 2.2Ta 2O 9 thin films

La modified SBT (Sr 0.8La 0.1Bi 2.1Ta 2O 9) thin films of different thickness were fabricated on Pt/Ti/SiO 2/Si substrates by the metalorganic decomposition technique. All the films were annealed layer-by-layer at 800 °C using a rapid thermal annealing furnace. X-ray diffraction analysis indicated that the relative intensity of the (2 0 0) diffraction peak [ I(2 0 0)/ I(1 1 5)] increased with the increase of the film thickness. Eventually, an a-axis preferentially oriented SLBT film was obtained. These results are discussed with respect to the anisotropy of the grain growth. The a-axis preferentially oriented SLBT film, whose relative intensity of the (2 0 0) peak [ I(2 0 0)/ I(1 1 5)] was 1.05, had a remanent polarization (2 P r) value of 21 μC/cm 2 and a coercive field (2 E c) value of 70 kV/cm under the electric field of 200 kV/cm.

Structure and electrical properties of sol-gel-derived (001)-oriented Pb[Yb1∕2Nb1∕2]O3–PbTiO3 thin films grown on LaNbO3∕Si(001) substrates

( 1 − x ) Pb [ Yb 1 ∕ 2 Nb 1 ∕ 2 ] O 3 – x Pb Ti O 3 (PYbN–PT, x=0.5) oriented thin films were deposited onto LaNiO3 (LNO)∕Si substrates by sol-gel processing. Highly (001)-oriented LNO thin films were prepared by a simple metal-organic decomposition technique when sample annealed at 650°C using a rapid thermal annealing. The room-temperature resistivity of LNO thin films was 0.65mΩcm. X-ray diffraction analysis revealed that the films of PYbN–PT were highly (001) oriented along LNO∕Si substrates. No pyrochlore phase was observed by X-ray diffraction and films had a uniform grain size of about 80–120nm. At 1kHz, the dielectric permittivity was 920 and dielectric loss is about 0.035. The ferroelectric films displayed good P-E hysteresis characteristic and better temperature stabilization compared with the films that have low Curie temperature.

Electron Transport and Microwave Noise in MBE- and MOCVD-Grown AlGaN/AlN/GaN

Microwave noise temperature, current, and dissipated power were investigated at room temperature in undoped AlGaN/AlN/GaN channels grown by molecular beam epitaxy and metal-organic compound vapour decomposition techniques. Samples with essentially the same electron density (1× 10 cm−2) and low-field mobility (1150 cm/(V s)) demonstrated considerably different behaviour at high electric fields. The effective hot-phonon lifetime, 300 fs and 1000 fs, respectively, was estimated for molecular beam epitaxy and metal-organic compound vapour decomposition samples. The expected anti-correlation of hot-phonon lifetime and hot-electron drift velocity was confirmed experimentally.

Dielectric and interface characteristics of SrTiO3 with a MIS structure

SrTiO3 (STO) films were deposited onto the ptype Si substrates by metalorganic decomposition (MOD) technique. The dielectric and interface characteristics of STO with a metalinsulatorsemiconductor(MIS) structure were investigated. The results showed that the dielectric constant was about 105 and the dissipation factor was lower than 001 for our STO films at a frequency of 10kHz. The excellent dielectric properties were attributed to the polycrystalline structure with good crystallinity. The fixed charge density Nf and the interfacetrap density Dit were calculated to be about 15×1012cm-2 and (14—35)×1012cm-2eV-1, respectively. Both Nf and Dit were mainly connected with an interface layer with low dielectric constant formed at the interface of Si/STO.

Effect of excess Pb on crystallinity and ferroelectric properties of PZT(40/60) films on LaNiO 3 coated Si substrates by MOD technique

Pb(Zr 0.4Ti 0.6)O 3 [PZT(40/60)] films were deposited onto LaNiO 3 (LNO) coated Si substrates by metal-organic decomposition (MOD) technique. Excess Pb was incorporated in the film by using excess Pb (2%–15%) in the solution. The crystallinity and ferroelectric properties of PZT films were investigated by using X-ray diffraction (XRD), RT66A test system and HP4194 impedance analyzer, respectively. Rayleigh law was employed to analyze the defect concentration in the films. The results show that all the PZT films show the (1 0 0) preferential orientation with complete perovskite structure except for the 2% film displaying some pyrochlore phase. The (1 0 0) preferential orientation is mainly attributed to LNO bottom electrode, which has the highly (1 0 0) preferential orientation. The 10% film shows the best polarization and dielectric properties. The remnant polarization and coercive field are about 10.1 μC/cm 2 and 73 kV/cm under an electric field around 330 kV/cm, respectively. And the dielectric constant and dissipation factor are about 656 and 0.022 at a frequency of 1 kHz, respectively. The good ferroelectric properties of the 10% film are mainly attributed to the low defect concentration in the film.

Structural, morphology and electrical studies of Sm-modified bismuth titanate thin films on Si (100)

Samarium-substituted bismuth titanate (Bi 3.15Sm 0.85Ti 3O 12 (BSmT)) thin films have been grown on n-type Si (100) substrates by metalorganic decomposition and spin-coating technique. X-ray diffraction and scanning electron microscopy (SEM) analyses confirmed that the crystallinity of the films increases with increasing annealing temperature and the optimum temperature was found to be 700°C. The Raman measurement showed an increase in structural distortion due to the changed ionic radius and atomic mass of Sm ions. The current–voltage characteristics displayed good insulating properties for a film annealed at 700°C for 1 h. The capacitance–voltage characteristic hysteresis curves revealed that the ferroelectric property sufficiently controlled the silicon potential. The measurements of the dielectric constant and dissipation factor of BSmT as a function of frequency exhibited excellent dielectric properties.

Structural and electrical properties of Sm-doped bismuth titanate thin films on Si (100) by metalorganic decomposition

Samarium-doped bismuth titanate (Bi 3.5Sm 0.5Ti 3O 12) thin films have been grown on n-type Si (100) substrates by metalorganic decomposition and spin-coating technique. X-ray diffraction analysis confirmed that the optimum temperature for the crystallinity of the films was 700 °C. The Raman measurement showed an increase in structural distortion due to the changed ionic radius and atomic mass of Sm ions. The electrical measurements were conducted on metal–ferroelectric–semiconductor (MFS) capacitors. The current–voltage characteristics displayed good insulating properties for a film annealed at 700 °C for 1 h. The capacitance–voltage curves revealed that the MFS structure had a memory effect.

Characteristics of La0.5Sr0.5CoO3 thin films fabricated by a simple metal-organic decomposition technique

Characteristics of La0.5Sr0.5CoO3 thin films fabricated by a simple metal-organic decomposition technique

Characteristics of La 0.5Sr 0.5CoO 3 thin films fabricated by a simple metal-organic decomposition technique

La 0.5Sr 0.5CoO 3 (LSCO) thin films were prepared using metal-organic decomposition method by spin-coating onto a Si (1 0 0) substrate. Both the structure and morphology of the films were analyzed by X-ray diffraction and atomic force microscope. The LSCO thin films annealed at 550–700°C for 1 h showed a polycrystalline phase and dense microstructure. The results indicate the LSCO film shows good metallic properties. The resistivity of LSCO films annealed at 650°C showed minimum value of 0.354×10 −4 Ω cm. Pb(Zr,Ti)O 3 (PZT) thin films grown on LSCO thin films showed no favored orientation and excellent ferroelectricity. The remanent polarization P r and coercive field E c are 19.5 μC/cm 2 and 1.38 V, respectively. Additionally, the PZT thin films deposited on LSCO substrate exhibited no significant degradation of switching charge at least up to 5×10 9 switching cycles at a frequency of 100 kHz below cycling fields of 5 V.

Effect of bismuth excess on the crystallization of Bi 3.25La 0.75Ti 3O 12 thin films on Pt/Ti/SiO 2/Si substrates

Bismuth lanthanum titanate (BLT) thin films with excess Bi contents were prepared onto a Pt/Ti/SiO 2/Si substrate by a metalorganic decomposition technique (MOD). The effect of Bi excess on the microstructure and ferroelectric properties was investigated. When a 10% of Bi excess was added, the BLT thin films showed a polycrystalline structure. The remanent polarization and dielectric constant decreased with more than 10% of Bi excess. Bi deficiency or Bi excess over 10% in the BLT films resulted in poor fatigue properties. This was attributed to the structure defects and a presence of a secondary phase, which coexists with a layered perovskite phase. The BLT thin films with 10% of Bi excess have the remanent polarization (2 P r) value of 25.66 μC/cm 2 and a coercive field of 84.75 kV/cm. The BLT thin films with 10% of Bi excess showed no fatigue even after 1 × 10 9 bipolar switching cycles.

Integrating Ba1-xSrxTiO3 Thin Films with Large Area, Affordable, Industry Standard Substrates for Microwave Applications

ABSTRACTThe US Army is actively pursuing technologies to enable transformation goals of a lighter, faster, more potent force via affordable, electronically scanned phased array antennas (ESA's) that will provide the means for achieving a high data rate with beyond-line-of-sight, mobile communications. In order to transition this technology to Army applications, it is important that the cost of each device be decreased from current technology. Traditionally, paraelectric, active thin films of magnesium doped barium strontium titanate, have been deposited on expensive ceramic (MgO, LaAlO3, SrTiO3, Al2O3) substrates, and compositionally designed for tunable microwave applications. By integrating an active, thin film material with a large area, low cost, microwave friendly substrate, the cost could be significantly reduced. While Si is not a suitable substrate for microwave applications, a low cost, microwave friendly, buffer layer on silicon would be.A high performance Ta2O5 thin film, passive, buffer layer on Si substrates has been successfully designed, fabricated, characterized, and optimized via metalorganic solution decomposition technique. The optimized Ta2O5 based thin film exhibited suitable microwave material properties, including an enhanced dielectric constant (εr = 45.6), low dielectric loss (tan δ=0.006), low leakage current, high film resistivity (ρ=1012 Ω-cm at E=1 MV/cm), excellent temperature stability (temperature coefficient of capacitance of 52 ppm/°C), and outstanding bias stability of capacitance (∼1.41% at 1 MV/cm). The permittivity and dissipation factor, also of extreme importance, exhibited minimal dielectric dispersion with frequency. The dielectric passive buffer layer film was typified by a uniform dense microstructure with minimal defects, and a smooth, nano-scale fine grain, crack and pinhole free surface morphology. At elevated processing temperature, there was negligible elemental interdiffusion at the interface between the substrate and buffer layer as verified by Rutherford Backscatter Spectroscopy and Auger Spectroscopy, ensuring long-term reliability of the heterostructure.By developing a passive, thin film material that is microwave friendly, we have demonstrated the direct integration of paraelectric active thin films with silicon substrates. This should allow phase shifter materials technology to be implemented across a wide spectrum of Army and commercial applications, specifically, affordable, mobile phased array antenna systems for a variety of DoD applications.

Nucleation and grain growth of SrBi 2Nb 2O 9 thin films

Bi-layered perovskite SrBi 2Nb 2O 9 (SBN) thin films have been deposited on Si (1 0 0) substrates by metalorganic decomposition technique. The SBN thin films were post-annealed at 700°C in a pre-heated annealing condition for the investigation of crystallization processes. A high-resolution transmission electron microscopy study showed a nucleation process and a grain growth mechanism of the SBN thin films from a fluorite-like phase to a Bi-layered perovskite phase. In an initial stage of the nucleation process, adjacent 10 nm-sized fluorite-like grains that were slightly misaligned were phase-transformed to a Bi-layered perovskite grain, when a lot of defects such as antiphase boundaries (APBs) were induced due to a little misalignment of the adjacent grains. After a further annealing process, the grain size of the Bi-layered perovskite phase becomes about 0.2–0.3 μm and many defects such as APBs have considerably diminished. This grain growth behavior is totally different from a conventional elliptical growth model, which occurred at the point of a grain growth mechanism and a change of the grain shape. Moreover, the surface morphology of the SBN thin film was remarkably improved compared with that of the elliptically grown SBN thin films.

FRAM 응용을 위한 건조온도에 따른 BLT 박막의 강유전 특성

Ferroelectric lanthanum-substituted Bi<TEX>$_4$</TEX>Ti<TEX>$_3$</TEX>O<TEX>$_{12}$</TEX>(BLT) thin films were fabricated by spin-coating onto a Pt/Ti/SiO<TEX>$_2$</TEX>/Si substrate by metalorganic decomposition technique. The grain size in BLT thin films were prepared with controlled by various drying process. The effect of grain size on the crystallization and ferroelectric properties were investigated by x-ray diffraction and field emission scanning electron microscope. The dependence of crystallization and electrical properties are related to the grain size in BLT thin films with different drying temperature. The remanent polarization of BLT thin film increases with the increasing grain size. The value of 2P<TEX>$_{r}$</TEX> and E<TEX>$_{c}$</TEX> of BLT thin film dried at 45<TEX>$0^{\circ}C$</TEX> were 25.9 <TEX>$\mu$</TEX>C/<TEX>$\textrm{cm}^2$</TEX> and 85 kV/cm, respectively. The BLT thin film with larger grain size has better fatigue properties. The fatigue properties revealed that small grained film showed more degradation of switching charge than large grained films.lms.s.

Preparation of (100)-Oriented LaNiO3 Oxide Electrodes for SrBi2Ta2O9-Based Ferroelectric Capacitors

LaNiO3 thin films were prepared on SiO2/Si and Pt/Ti/SiO2/Si substrates using a modified sol-gel technique. To decrease the annealing temperature, LaNiO3 thin films were annealed layer-by-layer in a rapid thermal annealing furnace. The effects of preheating temperature and annealing temperature on the crystallographic orientation and resistivity of LaNiO3 thin films were studied respectively. (100)-oriented LaNiO3 thin films can be formed on SiO2/Si and Pt/Ti/SiO2/Si substrates at an annealing temperature of 600°C. The typical room-temperature resistivity of the (100)-oriented LaNiO3 thin films deposited on SiO2/Si substrates is about 4.7×10-4 Ω·cm. To verify the function of LaNiO3 thin films as the bottom electrodes of ferroelectric capacitors, SrBi2Ta2O9 thin films were fabricated on LaNiO3-coated Pt/Ti/SiO2/Si substrates by the metal organic decomposition technique. No evident fatigue was observed for an SrBi2Ta2O9 thin film annealed at 600°C, although its remanent polarization is not as large as that for the SrBi2Ta2O9 thin films deposited directly on Pt/Ti/SiO2/Si substrates.

Synthesis of High Dielectric Constant Titanium Oxide Thin Films by Metalorganic Decomposition

Titanium-containing alkoxide (Ti[i-OCH(CH3)2]4) dissolved in 2-methoxyethanol was directly deposited onto silicon by the metalorganic decomposition (MOD) technique. Titanium oxide (TiO2) thin films are formed uniformly on Si after high-temperature annealing. Raman and X-ray diffraction measurements indicate that the structure changes completely from anatase to rutile phase at an annealing temperature of 700°C. During the crystallization, however, the reaction starts at the TiO2/Si interface, resulting in the formation of interfacial SiO2 layer with a thickness of 2.6 nm. In contrast, the TiO2 thickness was fairly constant. The capacitance-voltage characteristics revealed that with annealing temperature, the dielectric constant increases to a maximum (εmax=48) at 700°C. However, the dielectric constant decreases again above 700°C due to the occurrence of interfacial SiO2 growth. For the well crystallized TiO2 films, the leakage current decreases to 7×10-8 A/cm2 at 2 MV/cm and the maximum breakdown field is 3.3 MV/cm. The TiO2 thin films formed by MOD are expected to act as a suitable dielectric in place of conventional thin SiO2 for future integrated circuits.

비휘발성 메모리 소자응용을 위한 과잉 Bi 첨가에 따른 BLT 박막의 강유전 특성

The effect of excess Bi contents on the ferroelectric properties of B <TEX>$i_{3.25}$</TEX> L <TEX>$a_{0.75}$</TEX> <TEX>$Ti_3$</TEX> <TEX>$O_{12}$</TEX> (BLT) thin films has been investigated. Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/ <TEX>$SiO_2$</TEX>/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10% excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of 326 and dielectric loss of 0.024. The BLT thin films showed little polarization fatigue test up to 3.5<TEX>$\times$</TEX>10<TEX>$^{9}$</TEX> bipolar switching cycling.

Perovskite structure development and electrical properties of PZN based thin films

Abstract Pb(Zn 1/3 Nb 2/3 )O 3 (PZN) is a well known relaxor ferroelectric with excellent dielectric properties for capacitor applications and electromechanical properties for sensor and actuator applications. The perovskite structure stabilization of PZN based ceramics and their respective thin films has limited their applications in these devices. The crystallization behavior and the development of the perovskite structure in PZN with the addition of Pb(Zr 0.47 Ti 0.53 )O 3 (PZT) thin films were investigated using a metal–organic decomposition technique. When the annealing temperature was higher than 600 °C, the perovskite phase crystallized together with a pyrochlore phase. The fractions of the perovskite structure were kept at approximately 80% if the annealing temperature was higher than 700 °C. Otherwise, a new phase appeared when the annealing temperature was approximately 900 °C. Using a lead oxide upper-layer coating technique, a highly 〈111〉 oriented PZN based thin film with ∼96% perovskite was prepared. The electrical properties of this thin film were characterized with the remnant polarization, P r =25 μC/cm 2 , and the dielectric constant, e ′=712, respectively.

Bi 20TiO 32 nanocones prepared from Bi–Ti–O mixture by metalorganic decomposition method

Bi 20TiO 32 in the form of nanocones are reported for the first time, which have been found during the formation of Bi 2Ti 2O 7 nanocrystals. Bi 20TiO 32 nanocones were prepared by metalorganic decomposition technique. From X-ray patterns, it was found that Bi 20TiO 32 is a metastable phase, and can transform gradually into Bi 2Ti 2O 7 phase with the annealing time increasing at a temperature of 550°C. The image of field emission scanning electron microscopy shows that the lengths of the nanocones are up to several micrometers and the diameters of cusps range from 20 to 200 nm. The studies of transmission electron microscopy show that the nanocones are crystalline Bi 20TiO 32. The growth mechanism of Bi 20TiO 32 nanocones has been proposed, which is similar to the vapor–liquid–solid growth mechanism.

Ferroelectric Characteristics of Bi 4−x La x Ti 3 O 12 Thin Films Crystallized at Low Temperetures

Recently, Bi 4 m x La x Ti 3 O 12 (BLT) has received much attention because it enables low crystallization temperature with a large remanent polarization. BLT films were prepared using a metal organic decomposition technique followed by a rapid thermal annealing (RTA) and a furnace annealing. The annealing of BLT was performed in the temperature range from 550 to 700C. In particular, BLT film annealed at 600C using the RTA tool and the furnace shows good ferroelectric characteristics. The BLT film annealed at 600C exhibits a large value of remanent polarization (22 w C/cm 2 at 250kV/cm), and a low leakage current density (7 2 10 m 7 A/cm 2 at 250kV/cm), a good endurance characteristics for up to 3.2 2 10 11 cycles at 250kV/cm at 85C. From an accelerated imprint test, the lifetime of hysteresis integrity is estimated to be over 10 years at 85C. In conclusion, BLT is the one of the promising material to achieve the high density FeRAMs.