Djordje Djukic

Electrokinetic flow control for composition modulation in a microchannel

A numerical and experimental study of the injection into a microchannel of a fluid with a spatially modulated composition is presented. The investigation employs test structures constructed in polydimethylsiloxane by standard replica molding. Fluid-flow simulations are compared to flow results obtained by fluorescence microscopy experiments. Results show that for a given channel dimension, the desired modulation of the solution composition is only possible below a threshold frequency. The value of the threshold frequency is dependent on channel size as well as flow rate. Experimental results are in accord with numerical simulations and theoretical considerations.

Compositional and structural changes in LiNbO3 following deep He+ ion implantation for film exfoliation

The physical mechanism of He-ion-based exfoliation in Z-cut LiNbO3 is investigated. Rutherford backscattering/channeling, nuclear-reaction analysis, and transmission electron microscopy are used to examine the compositional and structural changes caused by deep ion implantation followed by thermal annealing. Lattice disruption, He-bubble formation, and Li depletion are observed in the implantation region, as well as the onset of exfoliation. The implications of these observations for the crystal ion slicing method are discussed.

Electro-optically tunable second-harmonic-generation gratings in ion-exfoliated thin films of periodically poled lithium niobate

The authors demonstrate that thin, single-crystal films fabricated by ion exfoliation of a bulk periodically poled LiNbO3 (PPLN) crystal reduced the tuning voltages for electro-optically tunable harmonic generation in PPLN devices. The tuning voltage of ±150V resulted in 0.5nm total tuning of the second harmonic signal in the authors’ 10-μm-thick device, compared to an order of magnitude higher tuning voltage value needed in a comparable bulk device.

Low-voltage planar-waveguide electrooptic prism scanner in Crystal-Ion-Sliced thin-film LiNbO3.

We report on the use of thin, i.e. 10 microm-thick, single-crystal LiNbO3, in low-voltage electrooptic prism scanners. These devices are fabricated by electric-field poling of a series of electrooptic prisms in a bulk crystal followed by high-energy ion implantation and subsequent etching of the poled samples. Such a single-crystal thin-film scanner, while having the same scanning functionality as with a bulk device, has an order-of-magnitude reduction in its required voltage; for example, a series of two prisms, of 2mm in total length, yields a deflection angle of 0.7 at 100V compared to more than 1.7kV for the same device in standard 200 microm-thick LiNbO3 wafers.

X-ray microbeam probing of elastic strains in patterned He+ implanted single-crystal LiNbO3

X-ray microprobing is used to investigate buried elastic strain resulting from deep He+ implantantion in LiNbO3. The implantation regions are defined lithographically and strain fields mapped with spatial- and energy-resolved x-ray microdiffraction to characterize the resulting structures. The structurally modified regions are found to retain their lateral lithographic definition, with the buried implantation being in strong compression.

Integrable wide-free-spectral-range Fabry–Perot optical filters using free-standing LiNbO 3 thin films

We demonstrate the use of free-standing thin films of a complex oxide for chip-scale optical filtering. The films are used as low-order etalons with very large free spectral ranges that exceed 6.78 THz (> 50 nm at 1550 nm) and use a small chip area (< 500 microm2) when they are integrated. The films are produced by crystal ion slicing; this process exfoliates a micrometers-thin layer of single-crystal optical material from a bulk parent by means of high-energy-ion implantation. The etalons, which are 10 microm thick with Ag deposited on both surfaces, are integrated into a silica-on-silicon waveguide block.

Fabrication and material properties of submicrometer SrTiO3 films exfoliated using crystal ion slicing

The crystal quality of submicrometer-thick SrTiO3 films that are formed by exfoliation from bulk crystals using deep implantation with H-ion beams is investigated. Nuclear reaction analysis and Rutherford backscattering/channeling are used to measure the implantation depth, crystal-lattice disruption, and surface damage prior to exfoliation. The surface profiles of the exfoliated films are examined with atomic force microscopy; the roughness is shown to be reducible to subnanometer levels with postexfoliation mechanical polishing.

Fabrication of patterned single-crystal SrTiO3 thin films by ion slicing and anodic bonding

A new technique for directly fabricating patterned thin films (<1μm thick) of fully single-crystal strontium titanate uses deep H+ implantation into the oxide sample, followed by anodic bonding of the sample to a Pyrex or Pyrex-on-Si substrate. The dielectric properties and crystal structure of such thin films are characterized and are found to be essentially those of the bulk single crystal.

Simulation and experimental validation of electroosmotic flow in a microfluidic channel

Steady electroosmotic and pressure driven flows in geometries of interest to biomacromolecular detection are considered. For both types of flow, experimental data are obtained by imaging fluorescent dye propagation. Numerical simulations are carried out using finite volume methods. Test structures are made of polydimethylsiloxane (PDMS) mold using the negative of the desired structure fabricated by SU-8 thick negative photoresist. Steady electroosmotic flow is governed by the Laplace equation under certain idealized conditions such as when the Helmholtz-Smoluchowski relation is satisfied at the inlet and outlet boundaries, and when the zeta potential is uniform across the domain. Electroosmotic fluid flow can be further idealized as two-dimensional when two parallel plates confine the flow. Such conditions are frequently encountered in many microfluidic devices. Numerical solutions of such an idealized two-dimensional electroosmotic flow are obtained. Equations describing the transient dye propagation are then solved in a straight channel followed by a downstream circular well. Effects of channel size, electric field and possible pressure driven flow components are explored.

Extremely thin, single-crystal films of LiNbO/sub 3/ fabricated using localized He+ ion-implantation

We demonstrate that extremely thin, i.e., /spl sim/2-3/spl mu/m, single-crystal films of LiNbO/sub 3/ can be formed on a wafer using patterned ion-implantation followed by chemical etching. Control of the membrane thickness and its waveguiding properties are demonstrated.