In an effort to discover a high-mobility p-type oxide, recent computational studies have focused on Sn2+-based ternary oxides. Ta2SnO6 has been suggested as a potentially useful p-type material based on the prediction of simultaneously high hole mobility and a wide range of synthesis conditions over which it is the energetically favored phase. In this study, we synthesized this material epitaxially for the first time and evaluated its properties experimentally. We measured the band gap to be 2.4 eV and attempted to substitutionally dope titanium for tantalum (TiTa ’) and potassium for tin (KSn ’) but found that both doped and undoped films were insulating. Amorphous Ta2SnO6 films were also grown via thermal atomic layer deposition (ALD) at 175 °C. Electrical characterization of the ALD-fabricated amorphous films found them to be insulating with an optical band gap of 2.24 eV. Density functional theory calculations indicate that, under MBE growth conditions, oxygen vacancies have a negative energy of formation in crystalline Ta2SnO6 when the Fermi energy lies near the valence band edge. These oxygen vacancies would lead to compensation of holes generated by TiTa ’ or KSn ’ dopants, which is consistent with our observations. We conclude that the direct growth of epitaxial p-type Ta2SnO6 films using MBE-accessible growth conditions is thwarted by the spontaneous formation of oxygen vacancies. While our growth conditions do not yield p-type films, we calculate that there are conditions under which Ta2SnO6 is the thermodynamically stable phase and spontaneous formation of compensating defects does not occur, motivating further studies with different synthesis techniques.

The lack of low-temperature (<200 °C) and easy-to-handle vapor deposition precursors for cadmium has been a limitation for cadmium chalcogenide ALD. Here, the cadmium amidinate system is presented as a scaffold for vapor deposition precursor design because the alkyl groups can be altered to change the properties of the precursor. Thus, the molecular structure affects the precursor stability at elevated temperature, onset of volatility, and reactivity. Cadmium bis-N,N-diisopropylacetamidinate (1) was synthesized and evaluated for its thermal stability, volatility, and reactivity–properties relevant to ALD precursors. Compounds 2, cadmium bis-N,N-diisopropyltertertiarybutylamidinate, and 3, cadmium bis-N,N-diisopropylbutylamidinate, are analogous to 1 and were synthesized by substituting the alkyl group on the bridging carbon during amidinate synthesis. All three compounds are volatile under reduced pressure, and thermal stability studies showed 1 and 3 to be stable at 100 °C in solution for days to weeks, while 2 decomposed at 100 °C within 24 h. Solution phase reactivity studies show 1 to be reactive with thiols at room temperature in a stoichiometric manner. No reactivity with either bis-silyl sulfides or alkyl sulfides was observed up to 110 °C over more than 3 days. Overall, the cadmium amidinate compounds presented here show potential as precursors in ALD/CVD processing, which can contribute to research critical for semiconductor processing.

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BACKGROUNDApplications with iconic user interfaces, (for example, interfaces with pulldown menus, radio buttons, and scroll bars), such as those found on Apple's Macintosh computer and the IBM PC under Microsoft's Presentation Manager, have become very popular, and for good reason. They are much easier to use than applications with traditional keyboardoriented interfaces, so training costs are much lower and just about anyone can use them. They are standardized between applications, so once you learn one application you are well along the way to learning another. The use of one reinforces the common elements between applications of the interface, and, as a result, you remember how to use them longer. Finally, for the developer, their support costs can be much lower because of their ease of use.While there are many benefits to iconic applications, ease of development isn't one of them. Their development, unfortunately for programmers, can take more than twice as long as traditional programs, with half of the code being dedicated to the user interface. Moreover, not anyone can develop a user interface; it takes a real specialist who knows the arcane syntax of iconic interface and window system programming, and who can handle the more difficult debugging process.In the microcomputer marketplace, iconic applications have been available for some time, however this is not so in the workstation marketplace. The workstation marketplace, with many more hardware platforms and players, hasn't had an environment which could support development of standardized iconic applications until recently.