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We present, in this paper, a non-conservative approach for building reliable magnetic field sensors based on the resistive and magnetoresistive responses of a varistor diode. These sensors can be built on a ceramic platform of a material which is a solid solution of the ilmenite–hematite consisting of 55 moles% ilmenite, FeTiO3, and 45 mole% of hematite, Fe2O3. This material is abbreviated as IHC 45. These sensors would be suitable for many applications in which a semiconductor Hall effect sensor is currently used. In addition, our ceramic sensors would be suitable for applications in high temperature, energy exploration and well logging, and radiation-dominant environments. The resistive mode sensor is expected to operate reliably and efficiently over the range of 0 $\text{m}\Omega $ /Oe at 0.5 mA which drops to a value of 24.2 $\text{m}\Omega $ /Oe at 2 mA. In the magnetoresistive mode, the sensor has the sensitivity of $142.6~\Omega $ /ln(Oe) and it is 15.6 $\text{m}\Omega $ /Oe at 2 mA. The magnetoresistive mode device also exhibits at room temperature a relatively large magnetoresistive ratio (MR%) of 57% at the modest field of just 4000 Oe making it potentially an attractive candidate for applications in spintronics and magneto-electronics.

The variation of the chemical composition and properties of PZT films as a function of oxygen pressure and laser fluence during pulsed laser deposition is used to tune the electrical properties of the PZT thin films. It is found that the deposition using a 248 nm laser fluence of 1.7 J/cm 2 and an oxygen pressure of 400 mtorr results the PZT films very similar to that of target material. Changing the laser fluences or oxygen pressure, affects the lead content of the deposited film. In the range of oxygen pressure 50–200 mtorr, the Zr/Zr+Ti and Ti/Zr+Ti ratio varies with oxygen pressure while the Pb/Zr+Ti ratio is almost uniform. Using oxygen pressure as a control parameter to tune the chemical compound and electrical properties of the deposited PZT films, the remnant polarization of the PZT films is tuned in the range of 6.6–42.2 µC/cm 2 , the dielectric constant is controlled in the range of 29–130, and the piezoelectric constant d 33 is controlled in the range of 3.82–4.96 pm/V for a 40 nm thick PZT film.

We report on the use of SrTiO3 films on GaAs(001) substrates grown by molecular beam epitaxy (MBE) as intermediate buffer layers for the heteroepitaxial growth of ferromagnetic La0.7Sr0.3MnO3 (LSMO) and room temperature multiferroic (ferroelectric/antiferromagnetic) BiFeO3 (BFO) thin films using the pulsed laser deposition technique. The exchange bias coupling effect in the BFO/LSMO heterostructure has been investigated. The magnetization measurements with field cooling exhibit a surprising increment in the magnetic moment with enhanced magnetic hysteresis squareness. This we believe is the consequence of exchange interactions between the antiferromagnetic BFO and the ferromagnetic LSMO at the interface. The integration of BFO materials with LSMO on GaAs substrates facilitated the demonstration of resistive switching based non-volatile memory (NVM) devices which can be faster with lower energy consumption compared to present commercial technologies. Ferroelectric switching observations using piezoresponse force microscopy show polarization switching demonstrating its potential for read–write operation in NVM devices. The ferroelectric and electrical characterization exhibits strong resistive switching with low set/reset voltages. Furthermore, we demonstrate a prototypical epitaxial field effect transistor based on multiferroic BFO as the gate dielectric and ferromagnetic LSMO as the conducting channel. The device exhibits a modulation in channel conductance with a high ON/OFF ratio. This work also demonstrates the first step towards the development of magneto-electronic devices integrated with a compound semiconductor.

This paper describes the properties and potential applications of a hybrid device consisting of a varistor diode and its embedded transistor whose origin lies in a magnetically tuned varistor diode. It is shown how the output current (or voltage) of a varistor based on a magnetic oxide semiconductor can be manipulated by the application of a magnetic field to produce an embedded device with characteristics similar to that of a conventional transistor. Following the tradition of microelectronics, we name it the HFET transistor where H stands for a magnetic field. Two types of embedded HFET devices are described here; one with the current-voltage (I-V) characteristics and the other with voltage-current (V-I) characteristics. Both I-V and V-I devices exhibit high degree of nonlinearly but only in the V-I mode of the HFET device well-developed saturation regions of output signals are found. The room temperature HFET in its V-I mode appears to be also a good electronic switch with well-defined “off” and “on” states. Saturated regions of output signals and electronic switching are the signature property of these HFET transistors along with the capacity of providing a good level of signal amplification. When cooled to 100 K the HFET V-I device appears to lose partially the electronic switching property but gain in signal amplifying potential. The HFET device in I-V mode does not display the defining properties of electronic switching but can amplify signals by almost 400%.

The paper describes the properties and potential applications of a novel hybrid varistor device originating from biased voltage induced modified nonlinear current-voltage (I-V) characteristics. Single crystal of an oxide semiconductor in the family of iron-titanates with the chemical formula of Fe2TiO5 (pseudobrookite) has been used as substrate for the varistor. The modifications of the varistor characteristics are achieved by superimposition of a bias voltage in the current path of the varistor. These altered I-V characteristics, when analyzed, reveal the existence of embedded transistors coexisting with the varistor. These transistors exhibit mutual conductance, signal amplification and electronic switching which are the defining signatures of a typical transistor. The tuned varistors also acquire the properties of signal amplification and mutual conductance which expand the range of applications for a varistor beyond its traditional use as circuit protector. Both tuned varistors and the embedded transistors have attributes which make them suitable for many applications in electronics including at high temperatures and for radiation dominated environments such as space.

In this paper, we explore the possibility of finding practical applications when the nonlinear current–voltage (I–V) characteristics of a varistor are modified by the application of external magnetic fields. With this goal in mind, varistors based on a pseudobrookite oxide semiconductor have been studied. Pseudobrookite (PsB) is a wide bandgap n-type semiconductor with the bandgap of 2.77 eV. It is also weakly ferromagnetic. The “voltage-dependent resistor” (VDR) mode of the magnetically-tuned pseudobrookite varistors offers an opportunity to advance magnetic sensor technology. The resistive and magnetoresistive parameters of PsB VDRs exhibit good responses to applied magnetic fields and they can therefore be the basis for the fabrication of simple yet practical magnetic sensors. These sensors can cover the range of magnetic fields between 0 and 4500 Oe with good accuracy, and could possibly be considered as a substitute for Hall Effect-based sensors for many applications. Also, due to their simple structure, they would be rugged and not susceptible to abuses. They may also be suitable for applications in hazardous environments such as high temperatures and atmospheres having the presence of radiation, such as neutrons, protons, etc. It is also possible that these novel sensors could be suitable for geological applications such as in well logging in search of energy sources.

The nonlinear current–voltage characteristics of a varistor device are modified with the help of external agents, resulting in tuned varistor–transistor hybrid devices with multiple applications. The substrate used to produce these hybrid devices belongs to the modified iron titanate family with chemical formula 0.55FeTiO3·0.45Fe2O3 (IHC45), which is a prominent member of the ilmenite–hematite solid-solution series. It is a wide-bandgap magnetic oxide semiconductor. Electrical resistivity and Seebeck coefficient measurements from room temperature to about 700°C confirm that it retains its p-type nature for the entire temperature range. The direct-current (DC) and alternating-current (AC) properties of these hybrid devices are discussed and their applications identified. It is shown here that such varistor embedded ceramic transistors with many interesting properties and applications can be mass produced using incredibly simple structures. The tuned varistors by themselves can be used for current amplification and band-pass filters. The transistors on the other hand could be used to produce sensors, voltage-controlled current sources, current-controlled voltage sources, signal amplifiers, and low-band-pass filters. We believe that these devices could be suitable for a number of applications in consumer and defense electronics, high-temperature and space electronics, bioelectronics, and possibly also for electronics specific to handheld devices.

Effect of Nb doping in the range of 0∼4 at% on 1 μm thick highly {100}-textured Pb1.1(Zr0.52,Ti0.48)O3 films has been investigated. Texturing of {100} as high as 97% is obtained for all the films due to the incorporation of a few nanometers thick Pb1.05TiO3 seeding layer. Overall, maximum polarization, remanent polarization, squareness, and coercivity decrease with Nb doping level. The PZT film with 3% Nb shows the maximum effective transverse piezoelectric coefficient −e 31,f of 12.9 C/cm2, which is 5∼15% higher than those films with other doping levels.

Some members of the modified iron titanate family show remarkable tolerance to radiation and are well suited for radhard electronics. Of particular interest are solid solutions of ilmenite–hematite (IH) represented by (1 − x) FeTiO3.xFe2O3 where x varies from 0 to 1; and pseudobrookite, Fe2TiO5 (PsB). These multifunctional oxides can be both ferrimagnetic and wide bandgap semiconductors, and can be exploited in a variety of ways in radhard electronics, microelectronics and spintronics technologies. In this paper we emphasize the potential applications of the modified Fe-titanates with special emphasis on: (a) response of the non-linear current–voltage (I–V) characteristics to a magnetic field; (b) how the introduction of a biasing voltage might be used to produce bipolar currents in circuits and fabrication of voltage tunable varistors; and (c) the response of non-linear current–voltage characteristics when irradiated with neutrons, protons and heavy Fe-ions. Based on these observations, we will identify a few applications for which we can make use of the unique multifunctional nature of modified Fe-titanates.

Pb(Zr 0.2 Ti 0.8 ) 1− x Nb x O 3 (PNZT) ( x = 0%, 1%, 2%, 3%, 4%) films with 1 μm thickness were deposited on a platinized silicon using the chemical solution deposition (CSD) method followed by rapid thermal annealing (RTA). X-ray patterns indicate that introduction of the first seeding layer significantly enhance the crystallization of films after RTA processing. Electrical characterization was performed on Pt/PNZT/Pt capacitors. In order to precisely determine the pyroelectric coefficients of the PNZT films, trapezium and sinusoidal temperature modulations were applied to Pt/PNZT/Pt capacitors while measuring the pyroelectric current signal. Pyroelectric voltage response of these films was measured with chopped IR radiation from a blackbody source tuned to equivalent of 400 °C. Results show that doping PZT with Nb significantly improves the ferroelectric and pyroelectric properties of these films. Films with doping level of 1 mol% of Nb exhibit the highest values of remnant polarization (49.33 μC/cm 2 ) and pyroelectric coefficient (4.6 × 10 −4 C/K m 2 ).

Nb-doped Pb(Zr20,Ti80)O3 (PZT) films were grown on both sides (side I and II) of Pt/TiOx/SiO2/Si(100)/SiO2/TiOx/Pt wafers by chemical solution deposition. The structures of these films were characterized by X-ray diffraction and scanning electron microscopy. The effective transverse piezoelectric coefficients of the poled films were in the range of 2.5∼ 6.4 C/m2. {100}-textured films show the highest value of e 31,f. A cantilever was actuated from side I (or II) and sensed from side II (or I). A linear relationship between charge and driving voltage was observed at a quasi-static frequency of 10 Hz. The resonant frequency of the cantilever was found to be 260 Hz. These results clearly indicate that double-sided PZT films are suitable for actuation and sensing of a device.

The ilmenite–hematite (1 − x) FeTiO3 · xFe2O3 solid solution system is considered to be a novel material for spin-electronics, microelectronics, high-temperature electronics, and radhard electronics. This paper focuses on thin films of composition x = 0.33 grown on (100) MgO single-crystal substrates using pulsed-laser deposition (PLD) under different argon–oxygen mixtures. The surface of the MgO was found to possess MgO2 crystals, yielding an orientation relationship, [001] MgO ∥ [011] MgO2 and (\( \overline{1} \)00)MgO ∥ (\( \overline{1} \)10) MgO2. The structural characterizations show that the films are crystalline and homogeneous without any secondary phase. The films show a weak and inclined (11\( \overline{2} \)0) growth epitaxy. A bandgap of 3.4–3.7 eV was obtained for these films from optical measurements carried out in the UV–visible region. Electrical measurements confirmed the semiconducting behavior. However, the resistivity was found to increase substantially on the slightest addition of oxygen into the chamber.

The role of ferroelectric LiNbO3 (LNB) in altering the frequency dependence of the capacitance of CaCu3Ti4O12 (CCTO) thin films has been investigated. A cost effective spin coating deposition process was used to integrate the oxide heterostructures onto silicon substrates. This study showed that the frequency stability of the CCTO/LNB structure was much improved when the crystallization conditions and physical dimension of each layer were optimized. To integrate this structure with current silicon technology, heterostructures of CCTO and LNB thin films were fabricated on HF terminated Si using chemical solution deposition. It was found that the order of deposition of the two layers was important for the structural quality of the heterostructures with the CCTO layer followed by the LNB layer being the preferred structure. In addition to improvement of the capacitance variation with frequency, the heterostructures also provide a path to tuning the frequency of operation.

The morphology, structure, and magnetic properties of the magnetic semiconductor ceramic Ilmenite–Hematite (IH), (1−x)FeTiO3–xFe2O3, were studied as a function of the composition x. The magnetic ordering temperatures that we observed were consistently higher than those reported previously and were, for most of the composition range, above room temperature. We rule out the formation of Fe clusters as the origin of the magnetic properties. These magnetic properties of IH ceramics, in combination with their semiconducting characteristics, render them promising for spin-electronic applications.

Ilmenite-hematite (IH) [(1−x)FeTiO3·xFe2O3] solid solutions are unique classes of materials showing both magnetic and semiconducting properties, which make them potential candidates for novel applications in microelectronics and spintronics. This paper focuses on their varistor behavior before and after exposure to 40 MeV and 10 MeV proton radiations up to a fluence of 5×1010 p/cm2. The IH films are tolerant to these irradiations with little significant change to the nonlinear current-voltage characteristics. The switching voltage of the devices is in the regime of practical applications, and the radiation tolerance makes these materials suitable for aerospace applications.

The effect of processing on the ferroelectric and piezoelectric properties of sol-gel grown Pb1.1Nb0.04Zr0.2Ti0.8O3 (PNZT) thin films was investigated. The effective d 31 piezoelectric coefficient of as-grown films was measured using piezoelectrically actuated cantilevers. The results indicate that films annealed after each layer possess a significant internal field, leading to high piezoelectric coefficients in the as-grown PNZT films. But the films annealed in the final step possess a very small internal field, and, consequently, small piezoelectric response.

Numerous studies have been carried out on the fabrication of ferroelectric lead titanate (PT) and lead zirconate titanate (PZT) thin films and their applications to pyroelectric sensors [1–3]. Not many efforts have been made to integrate the films with silicon technology. In this article, we report on the growth of lead-zirconium-titanates films doped with niobium (PNZT) by a sol-gel method on platinized Si substrates along with its characteristics for use in infrared sensor applications.

Heterostructures of ferroelectric antimony sulpho iodide (SbSI) and colossal magnetoresistive La 0.67 Ca 0.33 MnO 3 (LCMO) have been grown on NdGaO 3 substrates by pulsed laser deposition (PLD) technique. The integrated structure, with SbSI acting as a gate insulator and LCMO as a semiconductor channel, exhibited field effect along with a channel modulation of about 10%. This ferroelectric field effect has been observed at a voltage of only 2 V. The field effect was non-volatile, and very little change was observed in the channel resistance after more than 2 h. Polarization switching tests showed a small polarization loss of about 5% after more than 10 7 bipolar switching cycles.

Current–voltage ( I – V ) characteristics of solid solutions of ilmenite–hematite (IH) (1− x )FeTiO 3 · x Fe 2 O 3 , with x varying from 0 to 0.45, were studied. All compositions except x =0 exhibit a low-voltage varistor behavior. The switching voltage for these devices was found to be well below 10 V, with the lowest value being about 2 V. The nonlinear coefficient, α , of the devices varied between 1.75 and 3.7. These results indicate that varistors based on some members in the family of IH are suitable for protecting the Si-based microelectronic circuits from surge of transient currents.

Polycrystalline samples of La0.67Ca0.33MnO3 were prepared by solid-state reactions by varying the pelletization force and the sintering temperature. Lowering the sintering temperature gave rise to smaller grains and increased the overall resistivity of the ceramic. Partial melting was observed in the ceramics sintered at higher temperatures (1400–1500 °C). Additionally, these ceramics showed two distinct resistivity peaks. The resistivity peak near the magnetic transition (TC) was sharp, whereas the second peak was a broad one observed below TC.

Varistor-like highly nonlinear current–voltage (I–V) characteristics were observed in the ceramics of colossal magnetoresistive La–Ca–Mn–O at room temperature, which is above its magnetic transition temperature. The switching voltage of all devices studied was less than 5 V with a nonlinearity coefficient a in the range of 2.6–32. The microstructure of the grains and the grain boundary region changes as the pelletization pressure and sintering temperature are varied. The contribution of grain boundary region to the electronic properties increases as the grains become smaller, which resulted in higher values of a and higher resistivity of the ceramic. This effect was observed at lower pelletization force and sintering temperature. It was also observed that higher values of a were associated with a higher switching voltage. D 2002 Elsevier Science B.V. All rights reserved.

Members of the family of ilmenite–hematite (1−x)FeTiO3·xFe2O3 have been found to exhibit interesting semiconducting behavior over a wide range of temperatures. Low-voltage varistors were recently produced using ceramic specimens. The objective of this work was to grow and characterize epitaxial films of some members of the family that can be used for fabricating p–n junction devices. Epitaxial films of the (1−x)FeTiO3·xFe2O3 series (x=0, 0.10, 0.20, 0.27, 0.35, 0.45) were grown on (0001) sapphire substrates using pulsed laser deposition. The films are c-axis-oriented and exhibit good epitaxy.

Films of ferroelectric antimony sulphoiodide (SbSI) were grown on platinized silicon substrates by pulsed laser deposition (PLD). The films were grown at room temperature and later annealed at 200-250 °C in air for crystallinity. The Curie temperature (T C ) of these films was 17-21 °C, whereas the peak dielectric constant was up to 5000. These films showed nonzero remnant polarization above T C up to a temperature of 40 °C and a low leakage current density of around 10 m 6 A/cm 2 at 2V. SbSI films were integrated with colossal magnetoresistive La 0.67 Ca 0.33 MnO 3 (LCMO) thin film, which acts as a p-type semiconductor. The LCMO-SbSI heterostructures, with SbSI as a ferroelectric gate, showed a channel modulation of about 10%.

We present a study of anisotropy of transport and magnetic properties in a La 1-x Ca x MnO 3 (x1/3) film prepared by pulsed-laser deposition onto a LaAlO 3 substrate. We found a non-monotonic dependence of magnetoresistance (MR) on magnetic field H for both H perpendicular and parallel to the film plane but perpendicular to the current. In the longitudinal geometry (when H is parallel to both the current and the film plane) the MR was negative at all fields below 20 kOe, as expected for colossal-magnetoresistance manganites. This rather complex behavior of MR manifests itself at rather low temperatures, far below the Curie temperature T c , which was close to room temperature. Two main sources of MR anisotropy in the film have been considered in the explanation of the results: (1) the existence of preferential directions of magnetization (due to strains stemming from the lattice film-substrate mismatch or other reasons); (2) dependence of resistance on the angle between current and the magnetization, which is inherent in ferromagnets. The transport and magnetic properties of the film correspond well to this view. In particular, the following angle dependence of MR is found: R(θ)/R(0) = 1 + δ an (T,H) sin 2 θ (where θ is the angle between the field and current directions in the plane normal to the film but parallel to the current). The temperature and magnetic field dependences of δ an (T,H) were recorded and analyzed. A clear magnetization anisotropy, that generally favors the magnetization in the film plane is also found. At the same time the recorded magnetization curves (as well as the MR data) indicate, that the film crystal structure should be inhomogeneous in such a way that various parts of the films have non-identical magnetic properties (with different directions of spontaneous magnetization). This hypothesis is supported by X-ray diffraction which revealed that the film is inhomogeneous in strain, lattice parameter and lattice orientation. This peculiar macroscopic-scale disorder is caused by a film-substrate interaction. The possible reasons for formation of such structure and its effect on MR anisotropy are considered.

With increasing integration density and shrinking geometry DRAM fabrication technology has remained at the forefront of semiconductor industry. The basic unif of a DRAM is a single MOSFET with a storage capacitor. Although dimensions are being reduced there is hardly any room for reduction in the cell capacitance. This calls for methods to improve the charge storage in the miniature devices. The search for high dielectric constant materials has led to the use of ferroelectrics for charge storage. Barium strontium titanate (Ba1-xSrxTiO3) (BST) has thus found a very important place in the fabrication of DRAMs. The metal organic decomposition (MOD) proces is a techniquer for the worth of inorganic films without processing in vacuum or going through a powder step. It is a simple process that is both fast and economical, with very minimal investment. Thin films of BST were deposited on platinized silicon substrates by the spin-on method. The films were then pyrolyzed and annealed. The films obtained w...

Films of Bi–Ca–Sr–Cu–O (BCSCO) superconductor of the Bi2CaSr2Cu2Ox composition have been grown by the liquid phase epitaxy method (LPE) using a partially closed growth chamber. The films were grown on (110) NdGaO3 substrates by slow cooling under optimized conditions below the peritectic melting point (885 °C) of Bi2CaSr2Cu2O8. Optimization of parameters, such as seed rotation, soak of initial growth temperature, and growth period, results in the formation of the 2122 phase of BCSCO. X-ray diffraction (XRD) measurements show that the films grown on (110) NdGaO3 have a preferred (11n) orientation. The best values of zero resistance transition (Tc0) and critical current density (Jc0) obtained for films grown on (110) NdGaO3 substrates are 87 K and 5.7 × 104 A/cm2 (at 20 K), respectively. The films grown at rotation rates of less than 30 and more than 80 rpm are observed to be associated with a subphase in the Bi2CaSr2Cu2O8 system. Electron microprobe analysis indicates the composition of this subphase to be Bi0.07Ca0.93Sr2Cu5O8. Higher growth temperatures (>860 °C) also encourage the formation of this phase.

We demonstrated the capability of MeV proton irradiation to promote chemical ordering processes in a solid at low temperature. We used the ilmenite–hematite solid solution system which allows estimation of the degree of ordering through measurement of its magnetization. Normally, ordering through diffusion would require high temperature annealing. At high temperatures, however, the equilibrium state would be less ordered and thus the achievable ordering incomplete. High energetic protons continuously transfer energy to the sample through electronic interaction which locally deposits large quantities of energy without a general increase of the sample temperature. This promotes diffusion processes which allow the system to relax towards the ordered equilibrium state.

Pb(Nb0.02Zr0.2Ti0.8)O3 thin films with thickness of 900nm were spincoated on platinized silicon substrate using the sol–gel method. X-ray diffraction and field emission scanning electron microscopy show that the films are highly a-axis-oriented with columnar structure. A large remnant polarization (Pr+) ∼92.2μC∕cm−2 was observed for as-grown films. The coercive field (Ec+) for these films was 159.3kV∕cm. Good pyroelectric properties are obtained as a result of large remnant and spontaneous polarization and their strong temperature dependence. The pyroelectric coefficient and figure of merit at room temperature (22°C) are 10.8×10−4Cm−2K−1 and 2.34×10−5Pa−1∕2, respectively.

The paper deals with the integration of well-known bismuth ferrite (BiFeO3) multiferroic oxide with GaAs semiconductor. First 5 nm ultrathin SrTiO3 films were grown on GaAs (001) substrates as an intermediate buffer layer by molecular beam epitaxy. Then, room temperature multiferroic BiFeO3 (BFO) thin films were deposited by pulsed laser deposition. X-ray diffraction measurement showed high quality epitaxial BFO films with pure (00l) orientation. The dielectric loss has been effectively suppressed and the saturated polarization–voltage (P–V) hysteresis loops were obtained. The ferroelectric domains switching was affirmed by piezo-response force microscopic studies. A large remnant polarization P r (~80 μC cm−2) combined with the enhanced magnetization (72 emu cm–3) at 300 K was achieved for the optimal growth conditions. The optical properties were measured using the ellipsometry technique for the BFO thin films. The thickness and optical constants of the BFO films were obtained by taking into consideration the dielectric parameters as described by the Tauc-Lorentz model. Finally, direct bandgap was estimated at 2.70 eV which is highly comparable to BFO films grown on different substrates.

Ilmenite-hematite (IH) is a wide-band gap semiconducting material with a potential for low-voltage varistor applications. The nonlinear characteristics of this material were investigated before and after exposure to high-energy neutron radiation. The typical current–voltage characteristics of a varistor device are retained in all our samples subjected to neutron radiation. However, the effect is more pronounced on the device parameters like the nonlinear coefficient (α) and switching field (Es). The crystallinity of the ceramic remains unaffected after irradiation. Our observations confirm that IH-based varistor devices can perform satisfactorily even in radiation dominant environments such as in space and nuclear reactors.

Bulk single crystals of potassium tantalate niobate, KTa1–xNbxO3, ferroelectric with different values of Ta/Nb ratios have been grown by temperature gradient transport technique (TGTT). The samples with different values of × were characterized by measuring their spontaneous polarization, dielectric constant and losses, pyroelectric coefficients, Curie temperatures and lattice constants. This paper presents the results of the crystal growth experiments, ferroelectric characterization techniques and properties of potassium tantalate niobate crystals.

A new method of crystal growth based on the travelling zone technique is successfully used to grow single crystals of Bi2CaSr2Cu2O8+x superconductor. Relatively large crystals of the order of 4 × 3× 1 mm3 dimensions can be grown by using a bridgman type crucible in the traveling zone setup. Identification of crystals is carried out by X-ray powder diffraction and energy dispersive X-ray spectroscopy (EDAX) analysis. Single crystal X-ray diffraction shows a superstrucutre along the b-axis of the crystal grwon from a Bridgman type crucible. Scanning electron microscopy (SEM) studies conducted on these crystals show extensive evidence of layer-growth patterns. Supersonducting properties of these crystals are determined by four-probe direct current (DC) resistance and alternating current (AC) susceptibility measurements.

A new member in the tungsten-bronze family of ferroelectric lead-potassium-niobate (PKN), with general formula Pb1-xK2xNb2O6, has been grown as bulk single crystal. Growth of PKN with charge composition x = 0.23 has been achieved using the Czochralski technique of crystal pulling. Large diameter boules were grown in platinum crucibles at temperatures between 1280 °C and 1300°C. Crystallographic studies were conducted using X-ray diffraction techniques. The samples were characterized for ferroelectric properties between 25 °C and 600 °C and for optical absorption. This paper presents the crystal synthesis and the results of ferroelectric and optical characterization.

Films of 80 K phase of BiCaSrCu-oxide superconductor referred as BCSCO have been grown from KCl-Bi2CaSr2Cu2O8+ϰ solutions at different growth temperature regimes by the LPE process. Twin-free single crystal substrates of NdGaO3 with (001) orientation are used for growing these films. The temperature range of 850-830°C is found to be the most favorable region for the formation of the 2122 phase of BCSCO. Above 850°C up to the peritectic melting point of the 2122 phase (885°C), formation of the 2122 phase is highly suppressed with the separation of Bi2CaSr2Cu2O8+ϰ into 2021, calcium copper oxide (Ca2CuO3 and CaCu2O3) and other non-superconducting phases. X-ray powder diffraction analysis is used to identify different phases of BCSCO films. Morphological examination of the films is carried out by scanning electron microscopy. The onset of transition of the 2122 phase films is observed at 90 K and zero resistance is reached at 83 K. Post-growth annealing has an adverse effect on the superconducting properties of the films.

Thin films of the 80 K-phase of BiCaSrCu-oxide superconductor having the composition of Bi2Ca1.05Sr2.1Cu2.19Ox and high degree of crystalline perfection have been grown on c-axis oriented twin free single crystal substrates of NdGaO3. This has been achieved by carefully establishing the growth conditions of the liquid phase epitaxy (LPE) experiments. The temperature regime of 850 °C to 830 °C and quenching of the specimens on the termination of the growth period are found to be pertinent for the growth of quasi-single crystalline superconducting BCSCO films on NdGaO3 substrates. The TEM analysis reveals a single crystalline nature of these films which exhibit 100% reflectivity in infrared regions at liquid nitrogen temperature.

We investigated the IV and CV properties of an [(FeTiO3)0.67 (Fe2O3)0.33] epitaxial thin film. The four point probe (4pp) measurements revealed that the material has a linear IV relation and has a resistivity of approximately 0.56 ω cm. In contrast, the two point (2pp) measurements are highly non-linear suggesting the existence of Schottky barriers. The CV data suggest that the material under the contacts is depleted. From the corrected CV data, the carrier concentration is found to be of the order of 1023/cm3.

Highly textured films of the 2-1-2-2 phase of BiCaSrCu-oxide superconductor with c axis perpendicular to the single-crystal substrates of defect-free neodymium gallate, NdGaO 3 have been grown by the LPE technique from supercooled KCl solutions. It is found that the optimization of charge preparation and growth temperatures play a crucial role in obtaining highly oriented films reproducibly. Crystalline orientation of as-grown films is confirmed by scanning electron microscopy and X-ray diffraction studies. The onset of the superconducting transition ( T c ) at 82 K is determined by four-point probe resistance versus temperature measurement.

The phenomenal growths of information technology and related fields have warranted the development of new class of materials. Multifunctional oxides, magnetic-semiconductors, multiferroics and smart materials are just a few examples of such materials. They are needed for the development of novel technologies such as spintronics, magneto-electronics, radhard electronics, and advanced microelectronics. For these technologies, of particular interest are some solid solutions of ilmenite-hematite (IH) represented by (1-x) FeTiO3.xFe2O3 where x varies from 0 to 1; Mn-doped ilmenite (Mn+3-FeTiO3) and Mn-doped pseudobrookite, Mn+3-Fe2TiO5 (PsB). These multifunctional oxides are ferromagnetic with the magnetic Curie points well above the room temperature as well as wide bandgap semiconductors with band gap Eg > 2.5 eV. This paper outlines: (a) processing of device quality samples for structural, electrical and magnetic characterization, (b) fabrication and evaluation of an integrated structure for controlled magnetic switching, and (c) the response of the two terminal non-linear current-voltage (I-V) characteristics when biased by a dc voltage. Subsequently, we will identify a few microelectronic applications based on this class of oxides.

Multifunctional nature of the Fe-Ti-oxides makes them attractive candidates for novel applications in which their coupled semiconductor, magnetic, dielectric and optical properties can be exploited. In particular, they appear to be good candidates for the emerging technologies such as spintronics, magneto-electronics, and radhard electronics. In this paper we deal mostly with pseudobrookite (Fe2 TiO5), both pure and Mn-substituted variety. Materials processing, structural, magnetic and semiconducting properties have been discussed in-depth. The temperature and magnetic field dependence on the non-liner I-V characteristics are established opening the possibilities for fabricating magnetically switched devices

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Thin films of antimony sulpho iodide (SbSI) were grown on platinized silicon substrates by the pulsed laser deposition method. As grown films were amorphous and annealing at 250 °C for 5 minutes introduced crystallinity in the films. Infrared reflectance measurements were done in the frequency range ∼ 500 – 5000 cm−1 (wavelength ∼ 2–20 μm). The reflectance measurements were taken at temperatures above and below the ferroelectric transition of SbSI ∼ 20° C. The index of refraction for a (121) oriented film was determined to be 2.83 ± 0.35 at a temperature of 25.6 °C, and 2.80 ± 0.35 at a temperature of 9.6 °C. For a (002) oriented film, the index was 3.82 ± 0.48 at a temperature of 26.5 °C, and 3.76 ± 0.48 at a temperature of 8.0 °C. Pyro-optic coefficients of 1.5 × 10−3 °C−1 for the (121) oriented film, and 3.2 × 10−3 °C−1 for the (002) oriented film were obtained. These results are consistent with measurements done in the visible region, and demonstrate the potential of SbSI as an infrared detector material.

The films of colossal magnetoresistive La0.67Ca0.33MnO3 (LCMO) and ferroelectric SbSI were grown by pulsed laser deposition method for fabricating their heterostructures. By varying the processing conditions during film growth and controlling subsequently the annealing conditions, the resistivity transport properties of the LCMO films could be greatly modified. Preliminary tests on the ferroelectric field effect transistor (FeFET) based on LCMO-SbSI heterostructure showed that the device behaves like a nonvolatile memory element. The FeFET showed a maximum channel modulation of ∼10% at room temperature, and the switching voltage was less than 2 V.