This paper describes the measurement results of piezoelectric harvesters with AlN as piezoelectric material. The output power harvested from mechanical vibrations has been measured on micromachined harvesters with different geometries. The resonance frequencies ranged from 200 up to 1200 Hz. A maximum output power of 60 µW has been measured at an acceleration of 2.0 g at a resonance frequency of 571 Hz; the power output is of the same level as obtained with devices based on PZT. The package of the harvester requires special attention, since air-damping can significantly decrease the maximum power output.

Micromachined thermopiles are considered as a cost-effective solution for energy harvesters working at a small temperature difference and weak heat flows typical for, e.g., the human body. They can be used for powering autonomous wireless sensor nodes in a body area network. In this paper, a micromachined thermoelectric energy harvester with 6 μm high polycrystalline silicon germanium (poly-SiGe) thermocouples fabricated on a 6 inch wafer is presented. An open circuit voltage of 1.49 V and an output power of 0.4 μW can be generated with 3.5 K temperature difference in a model of a wearable micromachined energy harvester of the discussed design, which has a die size of 1.0 mm × 2.5 mm inside a watch-size generator.

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Large polycrystalline silicon (poly-Si) grains with a diameter of 1.8 mm are successfully prepared by excimer laser crystallization (ELC) of a sputtered amorphous silicon (-Si) film at a maximum process temperature of 100 C. By pulsed DC magnetron sputtering, -Si is deposited on a non-structured oxidized wafer. It is found that the -Si film deposited with a bias is easily ablated during ELC, even at an energy density below the super lateral growth (SLG) region. However, the -Si film deposited without a bias can endure an energy density well beyond the SLG region without ablation. This zero-bias sputtered -Si film with a high compressive stress has a low Ar content and a high density, which is beneficial for the suppression of ablation. Large grains with a petal-like shape can be obtained in a wide energy density window, which can be a result from some fine crystallites in the -Si matrix. These large grains with a low process temperature are promising for the direct formation of system circuits as well as a high-quality display on a plastic foil.

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