Morphology and Curie temperature engineering in crystalline La0.7Sr0.3MnO3 films on Si by pulsed laser deposition

Abstract

Of all the colossal magnetoresistant manganites, La 0.7 Sr 0.3 MnO 3 (LSMO) exhibits magnetic and electronic state transitions above room temperature, and therefore holds immense technological potential in spintronic devices and hybrid heterojunctions. As the first step towards this goal, it needs to be integrated with silicon via a well-defined process that provides morphology and phase control, along with reproducibility. This work demonstrates the development of pulsed laser deposition (PLD) process parameter regimes for dense and columnar morphology LSMO films directly on Si. These regimes are postulated on the foundations of a pressure-distance scaling law and their limits are defined post experimental validation. The laser spot size is seen to play an important role in tandem with the pressure-distance scaling law to provide morphology control during LSMO deposition on lattice-mismatched Si substrate. Additionally, phase stability of the deposited films in these regimes is evaluated through magnetometry measurements and the Curie temperatures obtained are 349 K (for dense morphology) and 355 K (for columnar morphology)-the highest reported for LSMO films on Si so far. X-ray diffraction studies on phase evolution with variation in laser energy density and substrate temperature reveals the emergence of texture. Quantitative limits for all the key PLD process parameters are demonstrated in order enable morphological and structural engineering of LSMO films deposited directly on Si. These results are expected to boost the realization of top-down and bottom-up LSMO device architectures on the Si platform for a variety of applications.

Textured Manganite Films Anywhere

“…Nevertheless, the magnetic and transport properties of LSMO can be tuned by various factors, such as external hydrostatic pressure 19 , oxygen stoichiometry 20,21 , Sr doping level 22 , as well as the strain effect 23 because of the sensitive lattice-spin-charge coupling. For example, epitaxial LSMO films exhibits lower T C than polycrystalline films of about 20 K 24,25 . In this way, it may be possible to tune magnetic and transport properties of films by inducing a texture or near-epitaxy of LSMO films on nonadapted substrates.However, the coexistence of optimized properties and its integration onto low cost substrates as silicon for the electronics industry or amorphous materials as glass is a current challenge required to overcome technological limitations.…”

Influence of alkylphosphonic acid grafting on the electronic and magnetic properties of La2/3Sr1/3MnO3 surfaces

“…La3d 5/2 spectra a were deconvoluted into three peaks [20], one main peak (dark gray curve) and two satellite peaks (gray curves). Sr3d 3/2 and Sr3d 5/2 spectra b can be deconvoluted into two pair of peaks corresponding to bulk (dark gray curves) and surface contributions (gray curves) [21].The average La/Sr ratio (~1.8) deviates slightly from the expected ratio (2.0) and according to literature it has been associated to a surface Sr rich phase [19,21,22,23,24,25]. We observe a decrease in the La/Sr ratio of about 5% after DPA grafting (~ 1.85 for bare LSMO and ~1.75 for LSMO/DPA samples).…”

Advances on Low-dimensional Perovskite Manganite Nanostructures

“…Jiang 等 [29] 研究了不同厚度 La 0.325 Pr 0.3 Ca 0.375 MnO 3 薄膜的磁性与电阻各向异性, 结果表明, 对于 30 nm 厚 的薄膜, 其各向异性电阻率(anisotropic resistivity, AR) 非常大(~10 5 %); 对于120 nm 厚的薄膜, 由于应变弛豫, 它的 AR 最大值显著降低(~2×10 3 %)。Nori 等 [30] 利用脉 冲激光沉积法在 Si(100)上制备了晶粒尺寸为 20~60 nm 的 La 0.7 Sr 0.3 MnO 3 薄膜, 并对其磁性能进行了表征。结 果表明, 晶粒致密排列的 La 0.7 Sr 0.3 MnO 3 薄膜居里温度 为 349 K, 而柱状晶粒组成的薄膜居里温度为 355 K, 这是目前已报道的沉积在 Si 衬底上 LSMO 薄膜最高的 居里温度。 最近, 人们对纳米结构的钙钛矿锰氧化物薄膜 的电磁输运特性亦进行了研究, 如 Hirooka 等 [31] 利 用原子力显微镜(AFM)辅助化学湿法刻蚀技术制备 了(La,Ba)MnO 3 纳米桥结构, 发现纳米桥的磁电阻 呈现 2 个数量级的变化。 近年来, Guo 等 [32] 采用 EBL 技术制备了不同宽度的 (La,Ca)MnO 3 薄膜微桥结 构, 电输运特性测量结果表明: 薄膜微桥宽度在 0.50 µm 以下, M-I 相变消失, 并且出现反常的正磁 电阻现象。…”