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16 Oct 2006

Volume 89, Issue 16, Articles (16xxxx)

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Appl. Phys. Lett. 89, 164101 (2006); http://dx.doi.org/10.1063/1.2362602 (3 pages)

Yen-Wen Lu and Chang-Jin(CJ) Kim
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Microhand for biological applications

Yen-Wen Lu and Chang-Jin(CJ) Kim

Appl. Phys. Lett. 89, 164101 (2006); http://dx.doi.org/10.1063/1.2362602 (3 pages) | Cited 17 times

Online Publication Date: 16 October 2006

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A microhand, approximately 1 mm in fist diameter, has been developed with microelectromechanical systems technology to mimic the human hand in microscale. The hand has multiple microfingers, composed of silicon phalanges and polymer-balloon joints. By pneumatically inflating and deflating the balloon joints, the microfingers perform the motions of flexion and extension. This device possesses attractive characteristics: (i) gentle but strong holding, (ii) out-of-plane enclosure, (iii) active grasping, (iv) being inert to surroundings, and (v) reliable monolithic construction. It operates in both air and aqueous environments, as well as demonstrates grasping, stretching, and detaching of soft objects in submillimeter scale for biological applications.
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87.80.-y Biophysical techniques (research methods)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
07.10.Cm Micromechanical devices and systems
07.07.Tw Servo and control equipment; robots

Feedback control and characterization of a microcantilever using optical radiation pressure

David M. Weld and Aharon Kapitulnik

Appl. Phys. Lett. 89, 164102 (2006); http://dx.doi.org/10.1063/1.2362598 (3 pages) | Cited 11 times

Online Publication Date: 16 October 2006

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The authors describe a simple method for feedback regulation of the response of a microcantilever using the radiation pressure of a laser. A modified fiber-optic interferometer uses one laser to read out the position of the cantilever and another laser of a different wavelength to apply a force that is a phase-shifted function of that position. The method does not require a high-finesse cavity, and the feedback force is due solely to the momentum of the photons in the second laser. The feedback phase can be adjusted to increase or decrease the microcantilever’s effective quality factor Qeff and effective temperature Teff. The authors demonstrate a reduction of both Qeff and Teff of a silicon nitride microcantilever by more than a factor of 15 using a root-mean-square optical power variation of ∼ 2 μW. Additionally, the authors suggest a method for determination of the spring constant of a cantilever using the known force exerted on it by radiation pressure.
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85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
37.10.Vz Mechanical effects of light on atoms, molecules, and ions
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Combined electron and focused ion beam system for improvement of secondary ion yield in secondary ion mass spectrometry instrument

L. Ji, Q. Ji, K.-N. Leung, and R. A. Gough

Appl. Phys. Lett. 89, 164103 (2006); http://dx.doi.org/10.1063/1.2362996 (3 pages)

Online Publication Date: 16 October 2006

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Using a combined electron and focused ion beam system to improve performance of secondary ion mass spectrometry instruments has been investigated experimentally. The secondary ion yield for an Al target has been enhanced to about one order of magnitude higher with the postionization induced by the low energy electrons in the combined beam. It can be further improved with the increase of electron beam current. When the combined beam is applied to insulating targets, sample charging is also eliminated. For Teflon targets, the secondary ion signal is increased by more than a factor of 20.
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07.75.+h Mass spectrometers
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Flory-Huggins swelling of polymer Bragg mirrors

Wolfgang Mönch, Jan Dehnert, Ewald Jaufmann, and Hans Zappe

Appl. Phys. Lett. 89, 164104 (2006); http://dx.doi.org/10.1063/1.2358811 (3 pages) | Cited 6 times

Online Publication Date: 17 October 2006

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Bragg mirrors have been fabricated from cross-linked standard optical polymers (polystyrene and polymethylmethacrylate). In an ambient containing organic solvents, these polymer multilayers swell, causing the transmission peak wavelength to shift towards higher wavelengths. The transmission spectra of these Bragg mirrors as a function of the solvent partial pressure in the surrounding atmosphere have been measured for different organic solvents. From the spectral signatures, we show that the mirror swelling is well described by a Flory-Huggins-type sorption behavior. This result suggests that polymer swelling may be used as a robust tuning principle for optical Bragg structures.
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42.79.Bh Lenses, prisms and mirrors
42.82.Cr Fabrication techniques; lithography, pattern transfer
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.70.Jk Polymers and organics

Microfluidic circuits with tunable flow resistances

Eric W. Lam, Gregory A. Cooksey, Bruce A. Finlayson, and Albert Folch

Appl. Phys. Lett. 89, 164105 (2006); http://dx.doi.org/10.1063/1.2363931 (3 pages) | Cited 12 times

Online Publication Date: 18 October 2006

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Microfluidic devices, due to their conveniently small size and the unique physicochemical behavior of fluids in microscale volumes, have become essential tools in many areas of science and technology. Fluid flow in microchannels, microvalves, and micropumps have many parallels with electrical current through wires, switches, and current sources of microelectronic circuits. The equivalent of a variable resistor, however, is still unavailable. Here the authors present addressable microarrays of deformable elements producing sixteen levels of flow resistance. Using a purely resistive electrical circuit analog, they predict the steady-state output of a three-inlet mixer.
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47.85.Np Fluidics
47.61.Fg Flows in micro-electromechanical systems (MEMS) and nano-electromechanical systems (NEMS)
47.60.-i Flow phenomena in quasi-one-dimensional systems
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Second inflection point of water surface tension

Y. J. Lü and B. Wei

Appl. Phys. Lett. 89, 164106 (2006); http://dx.doi.org/10.1063/1.2364167 (3 pages) | Cited 9 times

Online Publication Date: 18 October 2006

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The classical molecular dynamics method is applied to simulate the surface tension of water over the wide temperature range from 193 to 398 K. The results show that the temperature dependence of surface tension obviously increases in supercooled region, and there exists a second inflection point in the surface tension-temperature curve at about 303 K similar to the first one at 525 K, which confirms the conjecture based on the experimental measurements. When the temperature approaches 180 K, the simulated surface tension displays a sharp rise like the anomalies of some bulk thermodynamic properties.
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68.03.Cd Surface tension and related phenomena
65.20.-w Thermal properties of liquids

Enhancement of quantum well intermixing on InP/InGaAs/InGaAsP heterostructures using titanium oxide surface stressors to induce forced point defect diffusion

A. François, V. Aimez, J. Beauvais, M. Gendry, and P. Regreny

Appl. Phys. Lett. 89, 164107 (2006); http://dx.doi.org/10.1063/1.2364058 (3 pages) | Cited 3 times

Online Publication Date: 19 October 2006

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Quantum well intermixing was studied on InP/InGaAs/InGaAsP heterostructures under stress induced by a TiOx surface stressor. Results provide a comparison of thermal emission wavelength shift and effective emission wavelength shift for samples intermixed with and without applied stress. It is shown that TiOx decreases the measured thermal shift depending on the amplitude of the induced stress. It is also shown that the diffusion of point defects created during ion implantation prior to TiOx stressor deposition is significantly enhanced. This results in an increase of the effective wavelength shift by up to 300%.
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66.30.Lw Diffusion of other defects
61.72.J- Point defects and defect clusters
61.80.Jh Ion radiation effects
68.65.Fg Quantum wells
78.60.-b Other luminescence and radiative recombination

Effects of interfacial organic layers on thin film nucleation in atomic layer deposition

Abhishek Dube, Manish Sharma, Paul F. Ma, and J. R. Engstrom

Appl. Phys. Lett. 89, 164108 (2006); http://dx.doi.org/10.1063/1.2360902 (3 pages) | Cited 7 times

Online Publication Date: 20 October 2006

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Atomic layer deposition (ALD) of titanium nitride (TiN) on silicon dioxide and silicon dioxide modified by self-assembled monolayers (SAMs) with different structures and functional terminations has been investigated employing molecular beam techniques. On the –CH3 terminated SAMs, growth is significantly attenuated over that observed on clean SiO2, more than an order of magnitude for the thicker SAMs, and involves islanded, nonuniform growth. ALD is also observed on SAMs with reactive end groups, –OH and –NH2, but growth is uniform and attenuated only by approximately a factor of 3, independent of the thickness of these SAMs.
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68.55.A- Nucleation and growth
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
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