Synthesis and characterization of La0.7Ba0.3MnO3-SnO2 bilayer using pulsed laser deposition technique

Full text: Manganite based p-n junction bilayers were deposited using pulsed laser deposition technique as this technique stands to be unique to grow stoichiometric and oriented films. These manganite based bilayers are interesting to study as they are expected to show rectifying properties over a wide temperature range and even work at high temperatures. In this context we have deposited p-type manganite La0.7Ba0.3MnO3and n-type SnO2 on Si (001) substrates. The La0.7Ba0.3MnO3 and SnO2 bulk samples were synthesized through chemical routes that were used as target material in the deposition chamber. Thin films were deposited in pulsed laser deposition chamber using KrF excimer laser (λ=248 nm tp ∼20 ns). Deposition of these bilayers was performed in two steps. In first step a thin layer (∼950 nm) of SnO2 was deposited on Si (001) substrate at 580 deg C in the oxygen partial pressure of 1.3x 10-4 Torr, the deposited samples were cooled to room temperature at same oxygen pressure. In the second step a part of this film was masked and then La0.7Ba0.3MnO3 film (∼ 950 nm) was deposited at 500 deg C in the oxygen partial pressure of 400 mTorr, the deposited samples were cooled to room temperature in 500 Torr oxygen ambient. In both of the cases laser energy density and pulse frequency was 2 J/cm2 and 10 Hz, respectively. The bilayers were further examined for the structural and transport properties. The films were characterized by various techniques such as x-ray diffractometry (XRD), atomic force microscopy and four probe resistivity measurements. Crystal structure was determined using XRD. The XRD pattern of La0.7Ba0.3MnO3 shows oriented growth, SnO2 exhibits polycrystalline growth on Si (001) substrate. Atomic force microscopy reveals that the surface of the La0.7Ba0.3MnO3-SnO2 films is smooth. Good rectifying characteristics were observed at room temperature, which projects promising applications of these bilayers as diode-like device. Possible scenario of the surface morphology of the bilayers and the transport properties will be discussed. These results indicate that this p-n junction may be developed into functional, strongly correlated electronic devices at room temperature