Solution processed ZnO homogeneous quasisuperlattice materials

Abstract

Heterogeneous multilayered oxide channel materials have enabled low temperature, high mobility thin film transistor technology by solution processing. The authors report the growth and characterization of solution-based, highly uniform and c-axis orientated zinc oxide (ZnO) single and multilayered thin films. Quasisuperlattice (QSL) metal oxide thin films are deposited by spin-coating and the structural, morphological, optical, electronic, and crystallographic properties are investigated. In this work, the authors show that uniform, coherent multilayers of ZnO can be produced from liquid precursors using an iterative coating-drying technique that shows epitaxial-like growth on SiO2, at a maximum temperature of 300 °C in air. As QSL films are grown with a greater number of constituent layers, the crystal growth direction changes from m-plane to c-plane, confirmed by x-ray and electron diffraction. The film surface is smooth for all QSLs with root mean square roughness <0.14 nm. X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) of electronic defects in the QSL structure show a dependence of defect emission on the QSL thickness, and PL mapping demonstrates that the defect signature is consistent across the QSL film in each case. XPS and valence-band analysis shown a remarkably consistent surface composition and electronic structure during the annealing process developed here.

Metal Composition and Polyethylenimine Doping Capacity Effects on Semiconducting Metal Oxide–Polymer Blend Charge Transport

“…It is known that when annealing/converting a metal oxide precursor to a MO film in air the uppermost surface of the film is typically denser since direct air exposure facilitates oxidation of the MO precursor and further facilitates film densification by release of gaseous byproducts . Such phenomena were also observed in other solution processed metal oxides. , Higher PEI loadings enhance this effect not only for the third layer but, when present, for the other two layers as well, and is clearly seen for all 3 wt% PEI-doped MO samples (Figure S21).…”

α-Fe2O3/ZnO heterostructure for enhanced photocatalytic and antibacterial activity

“…A careful analysis of the VB region (figure 9) of the XPS spectra of the α-Fe 2 O 3 /ZnO heterostructure indicates that the VB consists of a two-peak structure with peaks positioned at 5.7 eV and 10.3 eV. The shape of the VB spectra of the heterostructure is similar to that of ZnO [49,50]. The intense peak at 10.3 eV shows the presence of zinc, since the Zn 3d position is at 10 eV.…”

(Invited) Material Porosity

“…The QSL number can also be controlled, allowing thickness control with up to 20 layers investigated. 139,140 All of these structures exhibit classical ZnO photoluminescence with a pronounced defect sub-gap emission. The dense ZnO portion of each bilayer of the QSL is formed during the pre-anneal drying stage, and the cumulative annealing time overall crystallized the thick multi-layered SQL to strongly c-axis oriented overall QSL structure.…”