SrRuO₃ Thin Films Grown under Reduced Oxygen Pressure

Abstract

SrRuO3 thin films are grown under reduced oxygen pressures between 10-6 Torr and 100 mTorr by pulsed laser deposition. The thin films grown at temperatures above 640° C and at a pressure of 10-6 Torr are characterized in terms of the lattice shrinkage due to oxygen deficiency. The resistivity increases and the temperature dependence changes to semiconductive from metallic as the oxygen pressure during growth is decreased. The Hall coefficient of the film grown at 740° C and at a pressure of 10-6 Torr is thirty times higher at low temperatures than at room temperature. The transport properties of the film are thought to result from the high carrier concentration but the low mobility due to the oxygen deficiency.

Surface layer of SrRuO3 epitaxial thin films under oxidizing and reducing conditions

“…Basic studies covered a wide range of properties of the material itself, 1,2 including such phenomena as quantum oscillations in electrical resistivity, 3 Hall effect sign reversal, 4 or magnetic anisotropy. 5 Other studies concerned changes induced by substitution of A-site element ͑Sr͒ with Ca, La, or Na; by substitution of B-site element ͑Ru͒ with Ti, Fe, Co, Mn, or Sn; [6][7][8][9][10] and also by introduction of oxygen deficiency 11 or ruthenium excess. 12 For instance a certain concentration of titanium turns the film into a paramagnetic insulator, 13 calcium doping suppresses ferromagnetism, while the material remains conductive, 14 and oxygen vacancies are reflected in the increase of resistivity of the film.…”

“…12 For instance a certain concentration of titanium turns the film into a paramagnetic insulator, 13 calcium doping suppresses ferromagnetism, while the material remains conductive, 14 and oxygen vacancies are reflected in the increase of resistivity of the film. 11 The metallic behavior of SrRuO 3 and its pseudocubic lattice constant, which is similar to many different perovskite related materials, allow a large area of applications. SrRuO 3 is not only a standard bottom electrode for the ͑Pb, La͒͑Zr, Ti, Nb͒O 3 and ͑Ba, Sr͒TiO 3 families of ferroelectric capacitors 15,16 but it is also a common metal layer in SrRuO 3 /YBa 2 Cu 3 O 7 Josephson junctions, 17 SrRuO 3 /Sr 2 YRuO 6 magnetic tunnel junctions, 18 and others.…”

“…Mostly pulsed laser deposition ͑PLD͒, using XeCl or KrF excimer laser, has been performed at deposition temperatures varying from 350 to 810°C and oxygen pressures in the range of 0.03-0.5 mbar. 11,25 Usually preparation conditions were optimized to obtain the lowest resistivity and a flat surface. The best films, with a room temperature resistivity of about 150-300 ⍀ cm, root mean square ͑rms͒ roughness about 0.1 nm, and rocking curves with full width at half maximum ͑FWHM͒ lower than 0.1°, have been produced at temperatures of 640-800°C and oxygen pressures of 0.1-0.4 mbar.…”

“…The best films, with a room temperature resistivity of about 150-300 ⍀ cm, root mean square ͑rms͒ roughness about 0.1 nm, and rocking curves with full width at half maximum ͑FWHM͒ lower than 0.1°, have been produced at temperatures of 640-800°C and oxygen pressures of 0.1-0.4 mbar. 11,26 Several other procedures, such as 90°o ff-axis sputtering 27 in temperature and pressure ranges of 300-680°C and 0.03-0.1 mbar, respectively, techniques requiring extremely low oxygen pressures ͑10 −6 -10 −3 mbar͒ such as magnetron sputtering, 28 ion beam sputtering, 12 or molecular beam epitaxy, 29 but also high pressure sputtering, 30 metal organic chemical vapor deposition, 31 or spin coating, 32 have been successfully applied. Most of them give results comparable to PLD.…”

Effect of lattice-misfit strain on the process-induced imprint behavior in epitaxial Pb(Zr0.52Ti0.48)O3 thin films

“…Comparatively, SRO, LSMO, and LNO are very stable and have different lattice constants. 14,15 Abe et al demonstrated that the lattice-misfit strain is important for the voltage shift in epitaxial BaTiO 3 (BTO) film. 8 In this letter, the process-induced imprint behavior in epitaxial Pb͑Zr 0.52 Ti 0.48 ͒O 3 films on the SRO, LSMO, and LNO electrodes was studied, and by controlling the lattice constant of the bottom electrodes, the lattice-misfit strain effect was addressed.…”