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La1−xSrxMnO3 films were grown at 450 °C by pulsed liquid-injection metalorganic chemical vapor deposition on silicon substrates. The films were amorphous and exhibited a high resistivity (> 10 kΩ cm). Different kinds of annealing (650 °C for 1, 3, 6, and 10 h, 800 °C for 15 mn, 900 °C for 5 mn, and rapid thermal annealings) were performed in order to achieve crystallization through both variations of nucleation and growth rates. X-ray diffraction and transmission electron microscopy were used to characterize the different microstructures obtained. After annealing, the perovskite La1−xSrxMnO3 (x∼0.3) phase was obtained. The resistivity of the films ranged within two orders of magnitude depending on the annealing temperature and time. The magnetoresistive properties were also recovered and similar to those obtained on as-grown polycrystalline films. The rapid thermal annealing process proved to be efficient: the amorphous films exhibited, after a 90 s flash-annealing, an ordering temperature of 340 K, a res...

The effects of the microstructure on the magnetoresistance of polycrystalline manganite (La1−xSrxMnO3) thin films have been investigated. The films have been grown by metalorganic chemical vapor deposition on silicon (001) substrates covered with a native silica layer. Different microstructures were obtained by varying the substrate temperature in the range (550–750 °C). The films exhibit a ferromagnetic/paramagnetic transition around 325 K. The grain size is in the range 20–100 nm and, for deposition temperature lower than 650 °C, weak links appear in the films as the grains are mostly noncohesive. The low-field contribution to the magnetoresistance is independent of the grain size in the studied range. A factor of ∼1.8 is gained in this contribution as the substrate temperature is lowered below 650 °C, which can be related to the occurrence of noncohesive grains in the films. The largest low-field magnetoresistance obtained is about 20% at 22 K (under 0.2 T). The high-field contribution to the total mag...

A new liquid source metalorganic chemical vapor deposition process has been developed in order to control precisely the amount of precursors vapors that is produced. Films of self-doped La0.8MnO3−δ have been deposited on LaAlO3 (012) substrates. X-ray diffraction measurements reveal an epitaxial growth. The as-deposited films exhibit both a ferromagnetic (Tc=200 K) and a metal–insulator (Tρ=130 K) transition. Postannealing experiments have been carried out and the results indicate the resistivity is considerably reduced, the temperature of transitions is raised to 320 K, and a magnetoresistance Δρ/ρ0=20% per tesla is obtained at 300 K in the 0–2 T range.

Thin‐film growth and compositional effects of c‐axis oriented YBa2Cu3O7−x (YBCO) thin films synthesized by metalorganic chemical vapor deposition have been investigated. The formation of single cation films using tetramethylheptanedionate precursors was shown to be mass controlled, exhibiting a ratio of deposited to evaporated species in the increasing order Ba, Y, and Cu. The physical properties of off‐stoichiometric YBCO films deposited on MgO substrates were measured in the compositional range 1.1≤Ba/Y≤2.3 and 1.5≤Cu/Ba≤4.6. While structural properties such as c‐axis values and rocking curves appeared unaffected to variations in cation stoichiometry, morphology was observed to be extremely sensitive even to slight changes in composition. Off‐stoichiometric layers with Cu/Ba≳1.5 were observed to exhibit Cu‐rich precipitates embedded in a 1:2:3 YBCO film matrix. The zero‐resistivity temperatures were above 77 K for all cation film compositions measured. However, sharp ac‐susceptibility transitions were r...

The magnetoresistance of step-edge junctions based on La0.7Sr0.3MnO3 films was investigated using a Wheatstone bridge geometry. Two types of step-edge structures were prepared: The step was either fabricated by ion-beam etching of SrTiO3 (001) substrates or by wet-chemical etching of an insulating NdMnO3 layer deposited on SrTiO3 (001). Both the magnetoresistive and insulating layers were deposited by injection-metalorganic chemical vapor deposition. The temperature dependence of the magnetoresistance was explored for both types of junctions in different field orientations. The largest low-field magnetoresistance was obtained when the step was formed directly in the substrate; it was observed up to room temperature (∼1% for an applied field of ∼0.05 T) and at 40 K, it increased ∼12% under an applied field of ∼0.1 T. The hysteretic behavior for the two types of junctions appeared to be very different.

The phosphorus redistribution in a WSi2/polycrystalline‐silicon structure after furnace annealing between 600 and 1000 °C was studied. When P is initially introduced into the polycrystalline‐silicon, a secondary ion mass spectroscopy analysis shows a nearly equidistribution of the dopant within the sandwich. When the silicide layer is phosphorus implanted, it has been clearly shown that with the refractory metal the dopant forms a tungsten phosphide compound more stable than WSi2 up to a critical temperature Tc. The stability of the phosphide increases with the implanted dose. A complete characterization of the additional phase was obtained by thermal annealing of W‐Si‐P powders. Several other interesting features on the redistribution of the dopant in the polycrystalline‐silicon/silicide structure have been established and discussed.

The electrical resistivity of monocrystalline TiSi2, TaSi2, MoSi2, and WSi2 has been measured from 4.2 to 1100 K. These disilicides are metallic, yet there is a remarkable difference in the temperature dependence of their intrinsic resistivities. TiSi2 and TaSi2 are found to exhibit a T5 dependence in the temperature range of 13

The cobalt reactivity on monocrystalline silicon has been studied for annealing temperatures lower than 500 °C. The techniques used were thermomagnetism measurements and transmission electron microscopy. The results demonstate that the reaction starts during deposition. During annealing the three types of formation kinetics were shown to exist as a function of temperature (20–220 °C, 220–370 °C, 370–420 °C). At the latter temperature the cobalt is completely transformed into CoSi and Co2Si.