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[摘要]：The atomic layer deposition of CaB2O4 was carried out using bis(tris(pyrazolyl) borate) calcium (CaTp(2)) and water as precursors. CaTp(2) melts at 280 degrees C, undergoes solid state thermal decomposition at 385 degrees C, and sublimed on a preparative scale at 180 degrees C/0.05 Torr in about 3 hours with 99.7% recovery and 0.2% non-volatile residue. Self-limited ALD growth was established at 350 degrees C with CaTp(2) and water pulse lengths of >= 2.0 and >= 0.3 s, respectively. An ALD window was observed from 300 to 375 degrees C, in which the growth rate was between 0.34 and 0.36 angstrom per cycle. The thin film compositions were assessed by elastic recoil detection analysis (ERDA) and X-ray photoelectron spectroscopy (XPS). The B/Ca ratios for CaB2O4 films deposited at 275, 325, 350, and 400 degrees C were 1.84(11), 1.85(11), 1.89(13), and 1.42(10), respectively, as determined by ERDA. Within the ALD window, hydrogen concentrations ranged from 0.22(2) to 0.35(4) atom% and the carbon and nitrogen concentrations were below the detection limits. XPS analyses on representative CaB2O4 thin films showed all expected ionizations. X-Ray diffraction experiments revealed that the as-deposited films were amorphous. The surface morphology was assessed by atomic force microscopy and scanning electron microscopy. The rms surface roughness of a typical 2 mu m x 2 mu m area for films deposited at 325 and 350 degrees C was 0.3 nm. Scanning electron micrographs of these films showed no cracks or pinholes. |
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