We present novel nanoscale bolometers made of lithographically defined platinum wires. The cores of our structures are
narrow wires with fixed width of 300 nm and length ranging from 300 nm to 17 μm. Some are significantly smaller in
size than the wavelengths they are exposed to from a 1200 K blackbody source. The response of the wire's resistance to
the external radiation reflects its temperature and can be monitored in real-time. Previously, we have reported a steep rise
in responsivity and detectivity with decreasing wire length under such infrared exposure, for a constant Joule power
dissipation in the wire (drive power). In this work, we aim to enhance the performance of the bolometers by changing
physical and driving parameters, i.e. the insulating layer thickness or the external bias. We find that after such
optimization, structures can reach a responsivity <i>R</i> of 4.5x10<sup>5</sup> V/W and a detectivity D* of 2.3x10<sup>10</sup> cmHz<sup>1/2</sup>/W. With a
reduced size and a high performance, these devices could improve the infrared sensors technology.
Some time ago a near-field optical imaging technique had been introduced (Appl. Phys. Lett. 73, 1669 (1998)), which achieves high spatial resolution and excellent sensitivity by exploiting the highly localized and mutual near-field interactions between a Au-nanosphere and a sharp Si-probe under evanescent field illumination. Specifically, the scattering of Au-nanoparticles is significantly enhanced by the presence of a sharp nanoscopic probe demonstrating that the probe acts as an efficient antenna. The present study focuses on the underlying physics of the original results by investigating more systematically nanoparticle-probe interactions: (1) The polarization pattern of the scattered field of an evanescent wave excited Si-probe is studied, which demonstrates that the probe scatters as a single dipole. (2) The enhanced scattering signal is measured as a function of sample size, which allows us to predict the signal strength for different size samples. (3) The wavelength dependence of the probe-sample scattering is investigated by exciting Au-nanospheres on (@543 nm) and off plasmon resonance (@633nm). The data shows a pronounced wavelength dependence reflecting the near-field spectrum of the Au-nanocrystals. (4) Finally, a simple, but intuitive model describing these mutual near-field interactions is presented, which explains qualitatively both the size and wavelength dependence of the enhanced scattering signals.