Joseph Ashley Taylor

Imaging nanostructures with coherent phonon pulses

We demonstrate submicron resolution imaging using picosecond acoustic phonon pulses. High-frequency acoustic pulses are generated by impulsive thermoelastic excitation of a patterned 15-nm-thick metal film on a crystalline substrate using ultrafast optical pulses. The spatiotemporal diffracted acoustic strain field is measured on the opposite side of the substrate, and this field is used in a time-reversal algorithm to reconstruct the object. The image resolution is characterized using lithographically defined 1-micron-period Al structures on Si. Straightforward technical improvements should lead to resolution approaching 45nm, extending the resolution of acoustic microscopy into the nanoscale regime.

Nonorthogonal wafer dicing for waveguide, microelectromechanical systems, and nanotechnology applications

We propose a technique to dice wafer using photolithography and deep reactive ion etch. We demonstrate our technique by dicing an eight inch wafer into 1.8×104 pieces of arbitrary shape and size. Our idea is suitable in dicing nano-chips and non-rectangular devices such as waveguide and microelectromechanical systems.

Nanoscale coherent acoustic phonon imaging

An ultrafast optical pump and probe technique known as picosecond ultrasonics is used to generate and detect coherent acoustic phonon pulses in nanostructured films grown on Si wafers. By detecting the phonons after they have diffracted across a millimeter thick wafer, it is possible to measure the scattered phonons in the acoustic far field. Numerical backpropagation algorithms can then be used in order to reconstruct the object which scattered the acoustic phonon pulses. We describe measurements and simulations of experiments performed on surface and sub-surface nanostructures. Results with ~500 nm image resolution are shown, and plans for improving that resolution by an order of magnitude will be described.

Nanoacoustics: propagation and imaging with THz coherent phonons

We investigate experimentally and theoretically the propagation of coherent acoustic phonon pulses generated in Si using ultrafast optical pulses. These acoustic pulses are shown to be applicable for two-dimensional nanoscale imaging. In a recent paper [1], we presented a proof-of-concept experiment which showed that it is possible to use coherent acoustic phonons for 2-D sub-micron-resolution imaging of metallic nanostructures fabricated on a semiconductor substrate. Single-cycle coherent phonon pulses are generated and detected using an ultrafast pump-and-probe technique known as picosecond ultrasonics [2,3]. The experimental arrangement is illustrated in Fig. 1. The object is located on one side of a 0.5 mm thick Si wafer and is heated with femtosecond optical pump pulses. Acoustic waves (peak frequency and bandwidth ~ 0.1 THz) launched from the object are then detected by time-delayed optical probe pulses at a number of positions on an Al transducer deposited on the opposite side of the wafer.

Nanoscale imaging with coherent acoustic phonon pulses

We describe ultrafast coherent acoustic phonon measurements of a latent photoresist pattern with 1 mum features that is buried beneath an A1 film. Simulation results for higher resolution measurements are also described.

Coherent acoustic phonons in silicon: propagation studies and imaging applications

We generate and detect coherent acoustic phonon pulses in Si using ultrafast optics. A unified model of diffractive, dispersive, and nonlinear propagation effects is developed and verified. Imaging using diffracted phonon pulses shows submicron resolution.

Nanostructure imaging with sub-THz coherent acoustic phonon pulses

We describe a novel imaging technique that employs coherent acoustic phonon pulses which are generated and detected by ultrafast optical methods. Sub-micron resolution images of Al lines lithographically etched on a Si substrate are shown

Imaging nanostructures with picosecond ultrasonic pulses

We describe a novel imaging technique that employs coherent acoustic phonon pulses which are generated and detected by ultrafast optical methods. Sub-micron resolution images of Al patterns lithographically etched on a Si substrate are shown.