Low-Temperature Plasma-Enhanced Atomic Layer Deposition of Tin(IV) Oxide from a Functionalized Alkyl Precursor: Fabrication and Evaluation of SnO2-Based Thin-Film Transistor Devices.

A bottom-up process from precursor development for tin to plasma-enhanced atomic layer deposition (PEALD) for tin(IV) oxide and its successful implementation in a working thin-film transistor device is reported. PEALD of tin(IV) oxide thin films at low temperatures down to 60 °C employing tetrakis-(dimethylamino)propyl tin(IV) [Sn(DMP)4] and oxygen plasma is demonstrated. The liquid precursor has been synthesized and thoroughly characterized with thermogravimetric analyses, revealing sufficient volatility and long-term thermal stability. [Sn(DMP)4] demonstrates typical saturation behavior and constant growth rates of 0.27 or 0.42 Å cycle-1 at 150 and 60 °C, respectively, in PEALD experiments. Within the ALD regime, the films are smooth, uniform, and of high purity. On the basis of these promising features, the PEALD process was optimized wherein a 6 nm thick tin oxide channel material layer deposited at 60 °C was applied in bottom-contact bottom-gate thin-film transistors, showing a remarkable on/off ratio of 107 and field-effect mobility of µFE ≈ 12 cm2 V-1 s-1 for the as-deposited thin films deposited at such low temperatures.

Surface modification of ZnMgAl-coated steel by dielectric-barrier discharge plasma.

In this study, ZnMgAl alloy coated steel sheets were exposed to a dielectric-barrier discharge plasma with different gas mixtures (Ar, Ar + 5% O2, Ar + 5% H2O). Five different plasma-induced processes were identified at the surface: (i) etching of aliphatic carbon groups, (ii) conversion of absorbed carboxylates to carbonates, (iii) field-induced migration of Zn and Mg towards the surface, (iv) increased oxide layer thickness, and (v) homogenization of the surface potential of the originally very heterogeneous alloy. The relative contribution of each process depended on the specific gas mixture. Peel-test studies showed that all atmospheric-pressure plasma treatments improved the adhesive properties of the alloy coating for two different adhesives (acrylate and epoxy amine). The highest improvement was associated to the case of Ar + 5% H2O gas mixture, where all described surface processes took place to a high degree.

Water assisted atomic layer deposition of yttrium oxide using tris(N,N'-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii): process development, film characterization and functional properties.

We report a new atomic layer deposition (ALD) process for yttrium oxide (Y2O3) thin films using tris(N,N'-diisopropyl-2-dimethylamido-guanidinato) yttrium(iii) [Y(DPDMG)3] which possesses an optimal reactivity towards water that enabled the growth of high quality thin films. Saturative behavior of the precursor and a constant growth rate of 1.1 Å per cycle confirm the characteristic self-limiting ALD growth in a temperature range from 175 °C to 250 °C. The polycrystalline films in the cubic phase are uniform and smooth with a root mean squared (RMS) roughness of 0.55 nm, while the O/Y ratio of 2.0 reveal oxygen rich layers with low carbon contaminations of around 2 at%. Optical properties determined via UV/Vis measurements revealed the direct optical band gap of 5.56 eV. The valuable intrinsic properties such as a high dielectric constant make Y2O3 a promising candidate in microelectronic applications. Thus the electrical characteristics of the ALD grown layers embedded in a metal insulator semiconductor (MIS) capacitor structure were determined which resulted in a dielectric permittivity of 11, low leakage current density (≈10-7 A cm-2 at 2 MV cm-1) and high electrical breakdown fields (4.0-7.5 MV cm-1). These promising results demonstrate the potential of the new and simple Y2O3 ALD process for gate oxide applications.