Search

Nanocomposite polymer films are a very diverse research field due to their many applications. The search for low-cost, versatile methods, producing regulated properties of the final products, has thus become extremely relevant. We have previously reported a bulk-scale process, dispersing granulated metal oxide nanoparticles, of both unary and multi-component nature, in a low-density polyethylene (LDPE) polymer matrix, establishing a reference in the produced films’ optical properties, due to the high degree of homogeneity and preservation of the primary particle size allowed by this method. In this work, unmodified, free-standing particles, namely zinc oxide (ZnO), titanium dioxide (TiO2), aluminum oxide (Al2O3), and silicon dioxide (SiO2) are blended directly with LDPE, and the optical properties of the fabricated films are compared to those of films made using the granulation process. The direct blending process evidently allows for control of the secondary particle size and ensures a homogeneous dispersion of the particles, albeit to a lesser extent than the granulation process. Despite the secondary particle size being comparatively larger than its granulated counterpart, the process still provides a regulated degree of deagglomeration of the free-standing oxide particles, so it can be used as a low-cost alternative. The regulation of the secondary particle size tunes the transmission and reflection spectra, in both unary and mixed oxide compositions. Finally, the direct blending process exhibits a clear ability to tune the energy band gap in mixed oxides.

We report a one-step fabrication technique of silicon nanowires using KrF excimer laser. Nanowires (NWs) are fabricated by redistributing the silicon mass within the sample without etching any of t...

We report the fabrication of an array of random Silicon nanocones using a KrF excimer laser. A 370 nm thick amorphous Silicon layer deposited on a glass substrate was used in the process. The fabricated nanocones showed a large and broadband absorption enhancement over the entire visible wavelength range. An enhancement up to 350% is measured at λ = 650 nm. Additionally, the laser irradiation caused the nanocones to crystallize. The effect of changing the laser parameters (i.e. energy density, time, and frequency) on the morphology and the absorption is studied and compared. Wide-angle anti-reflective properties have been observed for the fabricated nanocones with less than 10% reflection for angles up to 60°. The major limitation of amorphous silicon thin film solar cells is the reduced absorption. This problem could be solved if light is trapped efficiently inside the thin film without the need of increasing the film thickness. The random array of nanocones presented in this work showed a substantial increase in absorption over a wide angle, were fabricated at a low cost and are easily scalable. This technique offers a fast approach which could significantly help in overcoming the absorption limitation.

In this work, we report a one-step fabrication of silicon nanocones from amorphous silicon substrates using excimer laser by melting and re-solidifying the deposited material. They show broadband absorption enhancement at multiple angles.

A novel fabrication technique of Silicon nanowires using excimer laser is developed in this work. Using one-step and easily scalable method, array of nanowires with broadband absorption enhancement are formed without etching the deposited material.

This work demonstrates, for the first time, the use of a post deposition laser annealing technique to realize operational SiGe MEMS devices at deposition temperatures as low as 210 °C. The patterned amorphous SiGe layers are treated by an excimer laser to induce crystallization. After the laser treatment, SiGe devices with good electrical and mechanical properties, such as contact resistivity values to a TiN electrode as low as 4.9 × 10 −7 Ω cm 2 and a strain gradient of −1.6 × 10 −6 μm −1 , are obtained. Devices such as an array of functional capacitive test structures and capacitive switches are realized.

This article reports on the development of thin films of p- and n-type bismuth telluride compounds which are suitable for microelectromechanical systems (MEMS) thermoelectric energy harvesters. Films were prepared by the pulsed laser deposition technique. It is shown that the thin films of binary Bi-Te alloys outperformed considerably their ternary counterparts. Furthermore, the highest thermoelectric figure of merit (ZT) was found to be 0.39 for the p-type Bi 32 Te 68 alloy, whereas the optimal n-type alloy was Bi 25 Te 75 , which was characterized by a relatively low stress gradient.

This work reports, for the first time, on the use of a post deposition laser annealing technique to realize SiGe MEMS devices at deposition temperatures as low as 210°C. It is demonstrated that by tuning the laser annealing conditions it is possible to realize SiGe devices with good electrical properties, including contact resistivity values to a TiN electrode as low as 4.9×10−7 Ωcm2, and good mechanical properties, with a strain gradient of −1.6×10−6 µm−1. Furthermore, this technique is used to fabricate an array of functional capacitive pressure sensors at low temperature.

Lowering the silicon germanium (SiGe) deposition temperature from the current 450°C to below 250°C will enable processing Micro Electro-Mechanical Systems (MEMS) on flexible polymer instead of on rigid silicon substrates or glass carriers. A major disadvantage of such a low temperature deposition is that the films are amorphous, with high hydrogen content and yield poor electrical and mechanical properties. To ensure films suitable for MEMS applications, a post-deposition laser annealing (LA) treatment is used. It is essential that the contact resistance between the SiGe MEMS structural layer and any lower electrode is minimized. In this work we investigate what beneficial effect a LA treatment can have on the contact resistivity of an initially amorphous SiGe MEMS structural layer with a bottom TiN electrode. We report a minimum contact resistivity of 2.14×10−3Ωcm2.

This work demonstrates, for the first time, the possibility of optimizing both electrical and mechanical properties of SiGe MEMS structural layers at low temperatures (≪ 250°C). Using selective laser annealing (LA), it is possible to reduce the strain gradient of SiGe films deposited at 210°C to −1.6×10−7 µm−1 and the electrical resistivity can be as low as 2.83 mΩ·cm.

This work is a step towards a viable process for poly-SiGe MEMS structural layers deposited at substrate temperatures below 250°C. Laser annealing was used for post-deposition layer treatment to realize poly-SiGe structural layers with the desired electrical and mechanical properties at low substrate temperatures. The technique uses a pulsed excimer laser beam for the local thermal treatment of a SiGe layer deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD) at 210°C. By tuning the laser treatment and the film deposition conditions, 1-1.8 μm thick films having an electrical resistivity as low as 14.1 mΩ∙cm and optimal strain gradient in the range of -4.3×10-6to +6.8×10-6μm-1were realized.