Controllable factors affecting the epitaxial quality of $$\hbox {LaCoO}_{3}$$ LaCoO 3 films grown by polymer-assisted deposition

Abstract

LaCoO 3 epitaxial films grown on (100) SrTiO 3 substrates were prepared by the simple polymer-assisted deposition successfully. Based on the characteristics by X-ray diffractometer, infrared spectroscopy and thermal analyzer, the influence of molecular weight of polyethyleneimine, heat-treatment condition, spin-coating speed on the crystallinity and epitaxial quality of LaCoO 3 films were discussed. It is found that the number of-NH groups plays a key role in the cationchelation of polyethyleneimine. Comparatively, more-NH groups existing in polyethyleneimine with larger molecular weight contribute to the improvement of epitaxial quality of LaCoO 3 epitaxial film. When polyethyleneimine begins to release the bound metal ions, higher heat-treatment temperature and a relatively rapid rate of heating can effectively prevent nucleus from growing in other orientations, thereby improving the epitaxial quality of film. Besides, the choice of spin speed will directly affect the thickness and surface roughness of the film, and may even affect the structure and performance of the film. The results will help to understand the cation-chelation mechanism of polyethyleneimine in the polymer-assisted deposition and extend this simple method for preparation of epitaxial films.

The Progress on Magnetic Material Thin Films Prepared Using Polymer-Assisted Deposition

“…Compared to other CSD methods, PAD has four obvious advantages: (1) it can realize low-cost growth of wafer-scale materials [ 2 , 3 , 4 , 5 , 19 , 20 , 60 ]; (2) it can accurately adjust the thickness [ 2 , 5 , 17 , 26 , 27 , 28 ] with the precursor concentration and spin-coating rates [ 2 , 26 ]; (3) it can prepare nanostructures with various morphologies, including TFs [ 1 , 35 , 36 ], composites [ 32 , 37 , 38 ], epitaxial heterostructures [ 19 , 28 , 31 , 39 , 40 , 41 , 42 ], NWs [ 43 , 44 ], hybrid fibers [ 11 ], feathers-like nanostructures [ 45 , 46 ], multilayered structures [ 47 ], and superlattices [ 1 , 47 ]; and (4) it can prepare single and complex metal oxides [ 8 , 30 , 31 , 34 , 48 , 49 , 50 , 51 , 52 , 53 , 54 ], metal nitrides [ …”

“…Notably, the orientation of LAO substrates has a significant effect on the epitaxial film magnetism, as in Figure 5 E. The LCO films with three different orientations show significantly different magnetic behaviors from the bulk, which is related to the biaxial compressive strain and the tetragonal distortion of CoO 6 octahedra ( Figure 5 H–K). It was also found that PEI molecular weight, heat treatment conditions, and spin-coating rate had significant effects on the crystallinity and epitaxial quality of LCO TFs [ 28 ]. In addition, epitaxial LCO TFs were obtained with PLD [ 69 ].…”

“…PAD is a chemical synthesis method in which metal ions coordinated with polymers are used as the precursor, and then the polymer is removed at a high temperature (approximately 500 • C) [1][2][3][4][5][20][21][22][23][24]. Owing to the unique properties of its polymer-involved process, PAD has five main advantages: (1) it can realize wafer-scale preparation of materials [2][3][4][5]19,20,25]; (2) it can accurately adjust the thickness in the range of sub-nanometer thickness to a thickness of hundreds of nanometers [2,5,17,[26][27][28];…”

“…(3) it is easy to produce materials doped with a variety of metal elements [29][30][31][32][33][34]; (4) it can prepare materials with different morphologies, including thin films (TFs) [1,35,36], composites [32,37,38], epitaxial heterostructures [19,28,31,[39][40][41][42], nanowires (NWs) [43,44], hybrid fibers [11], feathers-like nanostructures [45,46], and superlattices [1,47]; and (5) it can prepare metal oxides [8,30,31,34,[48][49][50][51][52][53][54], metal nitrides [13,15,[55][56][57], metal carbides [14,58], single-element materials [12,16,59], transition metal chalcogenides (TMDs)…”

“…PAD is a chemical synthesis method in which metal ions coordinated with polymers are used as the precursor, and then the polymer is removed at a high temperature (approximately 500 °C) [ 1 , 2 , 3 , 4 , 5 , 20 , 21 , 22 , 23 , 24 ]. Owing to the unique properties of its polymer-involved process, PAD has five main advantages: (1) it can realize wafer-scale preparation of materials [ 2 , 3 , 4 , 5 , 19 , 20 , 25 ]; (2) it can accurately adjust the thickness in the range of sub-nanometer thickness to a thickness of hundreds of nanometers [ 2 , 5 , 17 , 26 , 27 , 28 ]; (3) it is easy to produce materials doped with a variety of metal elements [ 29 , 30 , 31 , 32 , 33 , 34 ]; (4) it can prepare materials with different morphologies, including thin films (TFs) [ 1 , 35 , 36 ], composites [ 32 , 37 , 38 ], epitaxial heterostructures [ 19 , 28 , 31 , 39 , 40 , 41 , 42 ], nanowires (NWs) [ 43 , 44 ], hybrid fibers [ 11 ], feathers-like nanostructures [ 45 , 46 ...…”