Electrochemical oxidation of La2CuO4 thin films grown by molecular beam epitaxy

Epitaxially Induced Defects in Sr- and O-doped La2CuO4Thin Films Grown by MBE: Implications for Transport Properties

“…The strontium-doped films were used to study the doping dependence of the penetration depth [26] and coherence length [27], while the oxygen-doped films were used to demonstrate the electrochemical oxidation of c-axis films [7,28] as well as local electrochemical lithography [8].…”

“…Hence this compound represents a model system in which oxygen diffusion can be readily studied. We have recently shown that this simple electrochemical process is also applicable for c-axis thin films [7,8,28]. However, we have also speculated that a particular type of microstructural feature is a prerequisite for the proper functioning of the electrochemical oxidation: the presence of planar faults [28].…”

“…While only the compounds containing chains, such as YΒa 2 Cu3 O 7 , Y1-x Ρrx Βa2 Cu3 O 7 and LaΒa 2 Cu 3 O 7 , require a very large uptake of oxygen (approx. from 6.0 to 7.0) during cooling [4], a similar process is necessary for other compounds, such as the La 2-x SrCuO4 [5] or La2 CuO 4+δ [6][7][8][9][10][11][12][13] cuprates, although their uptake of oxygen is much smaller (x/2 and 5, respectively). It is difficult to give an absolute estimate of the precise oxygen content of thin films.…”

Molecular beam epitaxy and microstructural study of La2−xSr1+xCuVerbist1, Milat2, Tendeloo3 et al. 1997Phys. Rev. B

“…16 Their appearance and density depend mainly on the type of substrate but some variation is observed even among identical substrates. We have recently shown that these defects are excellent channels for oxidation both under electrochemical oxidation conditions 18,25,26 and during standard annealing procedures. The presence of these defects generally leads to well-oxidized thin films, but the variation in planar fault density from sample to sample can cause significant fluctuations.…”

“…[25][26][27] To characterize the electrochemical activity of a film, an I(E) cycle is performed; i.e., a voltage is applied between the sample ͑working electrode͒ and the reference electrode, while the current between the counterelectrode and the working electrode is measured. For a typical 214 thin film grown on STO, the voltammogram of an area (S g ϭ0.8 cm 2 ) between 0.35 and 0.72 V exhibits three different regions ͓Fig.…”