Focused ion beam milling of microchannels in lithium niobate

Abstract

We present experimental and simulation results for focused ion beam (FIB) milling of microchannels in lithium niobate in this paper. We investigate two different cuts of lithium niobate, Y-and Z-cuts, and observe that the experimental material removal rate in the FIB for both Y-cut and Z-cut samples was 0.3 lm 3 /nC, roughly two times greater than the material removal rate previously reported in the literature but in good agreement with the value we obtain from stopping and range of ions in matter (SRIM) simulations. Further, we investigate the FIB milling rate and resultant cross-sectional profile of microchannels at various ion beam currents and find that the milling rate decreases as a function of ion dose and correspondingly, the cross-sectional profiles change from rectangular to V-shaped. This indicates that material redeposition plays an important role at high ion dose or equivalently, high aspect ratio. We find that the experimental material removal rate decreases as a function of aspect ratio of the milled structures, in good agreement with our simulation results at low aspect ratio and in good agreement with the material removal rates previously reported in the literature at high aspect ratios. Our results show that it is indeed easier than previously assumed to fabricate nanochannels with low aspect ratio directly on lithium niobate using the FIB milling technique.

Acoustic Nanofluidics via Room‐Temperature Lithium Niobate Bonding: A Platform for Actuation and Manipulation of Nanoconfined Fluids and Particles

“…[70] Further, elastomers like PDMS strongly attenuate SAW, drastically reducing the acoustic energy that eventually makes its way into the fluid present in the PDMS-based channel. [73][74][75][76][77] In one such study, Sridhar et al produced nanofluidic channels with characteristic length scales of about 100 nm using FIB machining, [78] a straightforward but unfortunately tedious machining method. Very anisotropic and easily fractured, inert to most chemical etchants, highly pyroelectric, and transparent to all but the shortest wavelengths of lasers, LN has been mostly used as an inert substrate upon which electrodes, functional materials, and microfluidics structures are deposited for the final device.…”

“…However, in limited studies, focused ion beam (FIB) milling has been used to machine structures in LN. [73][74][75][76][77] In one such study, Sridhar et al produced nanofluidic channels with characteristic length scales of about 100 nm using FIB machining, [78] a straightforward but unfortunately tedious machining method.…”

Integrated opto-microfluidics platforms in lithium niobate crystals for sensing applications

“…Moreover, the recent development of techniques able to modify this material at a micro-and nanometer scale has led to a progressive increasing interest in it by the side of both the scientific and the industrial communities, thus promoting theoretical and experimental studies on pure and doped LiNbO 3 crystals. Recently lithium niobate has been also proposed as candidate for application in opto-microfluidic technology [19,20,21], thus combining the tools typical of microfluidics with the potentialities offered by this material. A further improvement could come from the integration on the same substrate of different functionalities such as a T-shaped droplet generator and optical stages to obtain a system able to perform on-site optical sensing processes such as those required in chemical and biological analyses.…”

Preface to Special Topic: Selected Papers from the Second Conference on Advances in Microfluidics and Nanofluidics and Asia-Pacific International Symposium on Lab on Chip

“…Sridhar et al 19 reported the work on focused ion beam (FIB) milling of microchannels in lithium niobate and found that it was indeed easier than previously assumed to fabricate nanochannels with low aspect ratio directly on lithium niobate using the FIB milling technique. CO 2 laser was applied to induce glass strip peeling off to form microchannels on soda lime glass substrates, as reported by Wang and Zheng.…”

“…It was a successful conference providing a highly interactive forum that brought together approximately 200 researchers of different disciplines from more than 20 different countries and regions. This special issue is dedicated to the original contributions that were presented at the conference and covers a wide range of research directions from both fundamental and practical application of microfluidics and nanofluidics, including acoustofluidics, 1,2 biosensor 3 and diagnosis, 4 dielectrophorsis, 5-7 droplet microfluidics, [8][9][10][11][12][13][14][15] electrokinetic flow 16,17 and electrophoresis, 18 micro-and nanofabrications, [19][20][21] as well as surface modification. 22 Beginning with acoustofluidics, Wang, Jalikop, and Hilgenfeldt 1 reported a bubble microfluidic device to filter, enrich, and preconcentrate particles of selected sizes through oscillating microbubbles of radius 20-100 lm driven by ultrasound.…”