Thin films

Characterizing thin oxide films deposited from solution precursors

The Center uses complementary electrical and physical/chemical characterization methods to assess the potential of films as alternatives to traditional vacuum processed oxides—as well as to investigate the impact of solution chemistry and processing on the film properties. The following three projects fall within the scope of the thin-films theme:

PROJECT: What distinguishes one amorphous structure from another amorphous structure? Amorphous thin films have become promising materials driving the development of next generation semiconductors in high technology. To-date, however, the chemistry relating synthetic routes to the resultant atomic structures and electronic properties remain virtually unknown. By combining expertise in a broad range of synthesis and analytical techniques (NMR, neutron and X-ray scattering, XAFS) with theory (classical pair potentials, DFT), this project seeks to determine if amorphous structures can be categorized rationally and to build foundational chemical principles that will define this field.

Amorphous Al2O3 produced by multiple synthesis routes (solution processing and atomic layer deposition) will serve as a case study to systemetize observed differences in electrical properties to critical structural differences, ultimately addressing how these structures and properties change with elemental substitutions.

PROJECT: Towards electronic structure design by transition metal doping of amorphous and polycrystalline oxide films. The electronic structure of mixed amorphous oxides consisting of alloys of transition metals and d-electron deficient metal oxides is of interest for fundamental and practical reasons.  Metal oxides are investigated or used for a variety of applications including passivation layers on solar cells, channel layers in TFTs, heterogeneous catalysts, and electrocatalysts. 

This project seeks to detail the electronic effects of adding transition metal dopants to large band-gap oxide films and to understand how electronic states introduced via doping can be used to control charge transport as a function of energy. Ultimately, the aim is to understand fundamental periodic trends of d state energies in a d0 metal oxide matrix and correlate it to the solid statet energy scale as a means of understanding the applicability of the scale to alloys or impurity dopants.

PROJECT: Elucidation of thin film evolution from solution deposition. With recent advances in solid-state NMR, the investigation of the coordination environment of aluminum and local chemistry of thin films has become possible. In particular, our recent work has shown that it is possible to track the coordination environment of aluminum in thin films using SSNMR techniques. In tandem with characterization of CSMC cluster precursors, tracking coordination environments from precursor to thin film will provide for a better understanding of film formation.

Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) data are correlated with SSNMR data. We will build a comprehensive picture of the evolution of the film with regards to local structure, oxide-hydroxide-nitrate content, and mass loss. Understanding the evolution of thin films will shed light on the effect of phosphorus in aluminum phosphate films (AlPO), lanthanum in lanthanum aluminum oxide films (LaAlO3), and on the final properties of the films annealed at different temperatures. This technique will also be employed to track the difference in structural evolution during humid annealing atmospheres.