Synthesis of novel material often times requires novel analysis and characterization techniques. The possibility of combining sputtering (SPU) and Atomic Layer Deposition (ALD) in the same chamber, Sputtering Atomic Layer Augmented Deposition (SALAD), has produced interesting meta-dielectric nanocomposite systems that have unique optical and electronic properties, which may find novel applications [1]. Scanning Microwave Impedance Microscopy (sMIM) is a relatively novel characterization tool which permits assessment of local impedance. More recently, the utilization of microwaves in the near field regime has been an exciting topic in the field of high-resolution microscopy. We were able to demonstrate 1 nm resolution using scanning Microwave Impedance Microscopy (sMIM) where a spontaneously forming water meniscus concentrated the microwave fields in small regions [2]. Here we analyzed numerically sMIM with Finite Element Method (FEM) to investigate complex metal-dielectric structures created in a SALAD system. sMIM measurements provide information on both real and imaginary parts of the reflected microwave signal, which can be associated with the local conductivity and permittivity. Yet, these quantities can be influenced by the local topography, so extraction of the electronic contribution is a challenge. In this work, we perform tip-surface distance scans in order to gain a better understanding of the substrate response and compare with the FEM results.
Here we present advances in the use of near field microwaves, in both high-resolution microwave microscopy of nanostructured materials, as well as on the processing of materials with high microwave power density in selected areas. For the former, we utilize a commercial Scanning Microwave Impedance Microscope (PrimeNano Inc.) and demonstrate 3nm feature size. We discuss the mechanisms for image contrast, as well as draw equivalent circuits for a variety of metallic, semiconductor and dielectric systems. For the latter, we built a homemade system that enabled the concentration of microwaves in areas smaller than 100um diameter. We report on the system performance, and demonstrate the use of the tool in monitoring materials changes as heating takes place, by measuring and analyzing the reflected microwave signal. In summary, we demonstrate the usage, limits and opportunities of harnessing microwave power in the near field to map and modify materials properties in small scales.
Depositing thin films is often limited to a specific deposition process by which precursors are transported and reacted in a deposition environment. In other words, a deposition environment in which two deposition processes are unified should offer a new perception of devising a thin film structure, which galvanizes our combining atomic layer deposition (ALD) and magnetron sputtering (SPU) in a single chamber – sputtering atomic layer augmented deposition (SALAD). The SALAD system offers advantages of both ALD capable of delivering precursor precisely and accurately and SPU versatile in choosing chemical elements. In this paper, the SALAD system is employed to deposit nanocomposites consisting of multiple pairs of an aluminum oxide thin film deposited by ALD and a copper thin film deposited by SPU. Optical properties collected from the nanocomposites show distinctive dispersion features to which the effective medium approximation does not seem to simply apply.
Processing methods employing laser are often used to tailor semiconductors. For example, crystallization of semiconductors is induced via the interaction between laser and semiconductors – laser crystallization. While laser crystallization is widely used in preparing thin films made of a single chemical element, extending its use for those containing multiple chemical elements (e.g., metal oxides) could unfold applications currently not achievable. In this paper, a continuous-wave laser diode with a micrometer-scale chevron-shaped beam profile – micro chevron laser beam (μ-CLB) – is exploited to crystallize non-single-crystal CuO thin films deposited on fused silica substrates. Resulting single-crystal Cu2O strips are studied to reveal their unique characteristics associated with key parameters of the crystallization process.
Ultra-thin ZnO films were grown by atomic layer deposition (ALD) at a temperature of 60C on Si substrates and Si substrates coated with ~20nm of Al2O3 also deposited via ALD at 60C. Ellipsometry indicated ZnO films ranging in thickness from ~0.5 nm to ~7 nm. Atomic force microscopy results showed ZnO nano-islands formed prior to the completion of conformal atomic layers. AFM scans of 1um and 10um areas were employed in this study. This low dimensional ZnO islanding phenomenon was observed in both substrate types but with different incubation periods. The ZnO nano-islands on both substrates varied in diameter from ~20nm to ~100nm, island height variation ranged from ~2nm to ~9nm. ZnO nano-island formation had little to no incubation period on the Si substrates treated with ~20nm of Al2O3, and island formation was observed within 10 ZnO ALD cycles and nano-island density peaked around 20 to 30 ZnO ALD cycles. The highest rms roughness measurement obtained was of 0.7756 nm and is attributed to high nano-island density. While on bare Si the incubation period is significantly longer with nano-islands taking greater than 50 ZnO ALD cycles to form and achieving highest rms roughness of 0.25 nm around 60-70 ZnO ALD cycles. These results demonstrate non-conformal ultra-thin film growth by ALD, a deposition method expected to yield conformal thin films.
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