Initiated chemical vapor deposition of polymer films on nonplanar substrates

Thin polymer films are deposited on nonplanar geometries via initiated chemical vapor deposition (iCVD). Films in microtrenches exhibit step coverage of 0.85 for the highest aspect ratio trench studied here. An analytical model shows that the sticking probability of the initiating radical is a function of monomer surface concentration and takes values between 1.1 × 10^− 2 and 5.0 × 10^− 2 for the conditions studied here. These results indicate that iCVD proceeds via reaction of a vapor phase initiating radical with a surface adsorbed monomer. The high degree of conformality allows iCVD to be used to create patterns with features less than 10 µm by physically masking the substrate.     

Mechanisms of quantum dot energy engineering by metalorganic vapor phase epitaxy on patterned nonplanar substrates

A novel technique for tuning the strength of quantum confinement in site-controlled semiconductor quantum dots (QDs) is introduced and investigated theoretically and experimentally. The method makes use of controlled local growth rates during metalorganic vapor phase epitaxy on patterned arrays of inverted pyramids. A model accounting for precursor migration and adatom incorporation predicts the tuning in QD thickness as a function of the pattern parameters. The results are in good agreement with experimental findings. This technique offers means for designing QD photonic structures with potential applications in QD-based cavity quantum electrodynamics and quantum information processing.     

Nanopatterning of crystalline silicon with anodized aluminum oxide templates

A novel thin film anodized aluminum oxide templating process was developed and applied to make nanopores with anisotropic etching on crystalline silicon through reactive ion etching, with the purpose of enhancing the anti-reflection of silicon substrates. A unique two-step anodizing method was introduced to create high quality nano-channels and it was demonstrated that this process is superior over a one-step anodization approach. It was found that pore to pore distance and pore density can be tuned by changing the applied potential within a range of 10–80 V. Optical characterization of the nanopatterned silicon showed an average 10% reduction in reflection in the UV–Vis wavelength range.     

CNDO studies on nonplanar conformations in somecis- andtrans-polybenzobisoxazoles and polybenzobisthiazoles

While essentially rigid in the axial direction, the rod-like polymerscis- andtrans- polybenzobisoxazole (PBO) and polybenzobisthiazole (PBT) do exhibit conformational flexibility with respect to rotations about the bonds between alternating phenylenes and heterocyclic groups. Since preparation of high-strength materials from these polymers requires a high degree of alignment, this flexibility should be important in this regard. CNDO/2 molecular orbital calculations were therefore carried out to obtain the conformational-energy profiles of related model compounds. Thecis- andtrans-PBO models prefer the coplanar conformation while the barrier to the perpendicular conformation is about 8.4 kJ mol^?1. Thetrans-PBT model prefers0 = 20° with barriers to the coplanar and perpendicular conformations of about 2.1 and 25.0 kJ mol^?1, respectively. iModel compounds ofcis-PBT are bowed in the crystalline state. The bond-strain energies apparently responsible for bowing are estimated by comparing the CNDO/2 energy of the observed “bowed” molecule to that of a ficticious planar form. The “bowed” form is more stable by a large amount, indicating that in-plane bond-angle and bond-length distortions are not sufficient to relieve bond strain. Bowing hence appears to be a necessary alternative to these mechanisms for relieving the considerable strain within the planar form.     

Extreme ultra-violet resists development concepts and performances

Recently published experimental results indicate that current extreme ultra-violet lithography (EUVL) patterning process seems to be very hard to meet the device manufacturing specification goals, such as resolution, line-width roughness, and sensitivity (RLS) simultaneously. To overcome trade-off limitations between RLS performances of resist, we have approached the problem in several ways. Regarding materials, to make a uniform resist film we applied living radical polymerization and purification to obtain evenly interacting polymer chains. To obtain perfectly miscible resist components, such as polymer, photo acid generator (PAG) and quencher, we have optimized their structures to have similar polarity range. Acid diffusivity factors are also controlled by the resist components properties, including polymer T(g) and photo-acid polarity. In EUVL process, we applied surfactant rinse process to reduce line-width roughness and pattern collapse. In this paper, we discuss the performance of our EUV according to our material development concepts, that is, resist film homogeneity and acid diffusion control in order to meet the device manufacturing specification goals, such as resolution, line-width roughness (LWR), and sensitivity.     

非平面界面的多层高分子复合材料吸声性能

主要研究非平面界面的新型多层高分子复合材料在不同温度和压力下的吸声性能。制备了非平面界面的新型多层高分子复合材料和平面界面的传统多层高分子复合材料, 并在声管中测试其吸声系数。结果表明, 在所研究的频率范围内, 新型多层高分子复合材料吸声系数大于传统的多层高分子复合材料吸声系数; 这种新型多层高分子复合材料吸声系数峰值随温度的升高向低频方向移动, 而随压力变化不大。因此, 合理设计多层高分子复合材料的界面形状可以提高复合材料的吸声性能。      

The interfacial roughness effect on spin-dependent transport in nonplanar junctions with double magnetic barriers

In this paper, we use the transfer matrix method to study the effect of roughness with nonplanar interfaces on spin-dependent transport properties in a magnetic tunnel junction, which consists of two ferromagnetic semiconductor barriers separated by a nonmagnetic (NM) layer. This trilayer is sandwiched between two NM electrodes. The roughness is modeled as a periodic corrugation interface. Based on the effective mass approximation, the spin-dependent transmission probability, and also the dependence of tunnel magnetoresistance (TMR) and electron spin polarization (SP) on the center nonmagnetic layer quantum well width are studied, theoretically, at several different temperatures. The numerical results show that the SP and TMR have an oscillatory behavior as a function of NM layer thickness and the interface roughness/islands degrade the transmission probability. Our results may be useful for the development of nanoelectronic devices.     

Experiments on level ice loading on an icebreaking tanker with different ice drift angles

A series of tests was performed with a laboratory-scale model ship to simulate the effects of ice load parameters on an icebreaking tanker. A model of the icebreaking tanker Uikku was mounted on a rigid carriage and towed through an unbroken ice sheet in the ice tank of the Marine Technology Group at Aalto University. Two ice sheets and 11 different experimental configurations were used. The carriage speed, heading angle of the model ship, and ice thickness were varied, and the forces, accelerations, ice cusp sizes, carriage positions, and ice pile dimensions under the intact ice sheets were measured.This paper includes results for the measurements of ice rubble loads against the model hull in the horizontal plane. Phenomena such as ice failure modes and ice rubble accumulation on the upstream side of the hull beneath the ice sheet were observed in some tests. The icebreaking lengths and dimensions of ice rubble were analyzed for some tests. The effects of towing speed, heading angle under the intact ice sheet in front of the hull, and the accompanying ice loads on the formation and build-up of ice rubble were analyzed. In addition, the evolution of ice rubble geometry, in cross sections and the horizontal plane, was investigated. There was good agreement over several orders of magnitude between the measured and calculated values of the lateral ice forces. These results are relevant to the modeling of ice loading on hulls and the design of moored or dynamic positioned structures for operation in ice-covered waters. Some parameters obtained from these tests can be used as input for future numerical simulations.     

Nanopatterning the electronic properties of gold surfaces with self-organized superlattices of metallic nanostructures

The self-organized growth of nanostructures on surfaces could offer many advantages in the development of new catalysts, electronic devices and magnetic data-storage media. The local density of electronic states on the surface at the relevant energy scale strongly influences chemical reactivity, as does the shape of the nanoparticles. The electronic properties of surfaces also influence the growth and decay of nanostructures such as dimers, chains and superlattices of atoms or noble metal islands. Controlling these properties on length scales shorter than the diffusion lengths of the electrons and spins (some tens of nanometres for metals) is a major goal in electronics and spintronics. However, to date, there have been few studies of the electronic properties of self-organized nanostructures. Here we report the self-organized growth of macroscopic superlattices of Ag or Cu nanostructures on Au vicinal surfaces, and demonstrate that the electronic properties of these systems depend on the balance between the confinement and the perturbation of the surface states caused by the steps and the nanostructures' superlattice. We also show that the local density of states can be modified in a controlled way by adjusting simple parameters such as the type of metal deposited and the degree of coverage.     

Friction of sea ice on sea ice

This paper presents the results from field tests on the friction of sea ice on sea ice performed in the Barents Sea and fjords at Spitsbergen. The effects of the sliding velocity (6 mm/s to 105 mm/s), air temperatures (− 2 °C to − 20 °C), normal load (300 N to 2000 N), presence of sea water in the interface, and ice grain orientation with respect to the sliding direction on the friction coefficient were investigated. The effect of the hold time on the static friction coefficient was also studied. The roughness of the ice surface is an important parameter that determines the value of the friction coefficient. Repeated sliding over the same track led to surface polishing and decreased the kinetic friction coefficient from 0.48 to 0.05. The studies showed that the friction coefficient is independent of the velocity when sliding occurs between natural ice surfaces. As the contacting surfaces became smoother, the kinetic friction coefficient started to depend on the velocity, as predicted by existing ice friction models. Both very high (~ 0.5) and low (~ 0.05) kinetic friction coefficients were obtained in the tests performed at high (− 2 °C) and low (− 20 °C) air temperatures. The presence of sea water in the sliding interface had very little effect on the static and kinetic friction coefficients. The static friction coefficient logarithmically increased with the hold time from ~ 0.6 at 5 s to 1.26 at 960 s. The results are discussed, and the dependences are compared with existing friction models.     

Nanopatterning with interferometric lithography using a compact /spl lambda/=46.9-nm laser

We report the imprinting of nanometer-scale gratings by interferometric lithography at /spl lambda/=46.9 nm using an Ne-like Ar capillary discharge laser. Gratings with periods as small as 55 nm were imprinted on poly-methyl methacrylate using a Lloyd's mirror interferometer. This first demonstration of nanopatterning using an extreme ultraviolet (EUV) laser illustrates the potential of compact EUV lasers in nanotechnology applications.     

Nonlinear and nonplanar dynamics of suspended nanotube and nanowire resonators

Previous works on suspended carbon nanotube and nanowire resonators assume a priori that they oscillate in a single plane. We explore the nonlinear dynamics of such resonators and demonstrate that they can suddenly transition from a planar motion to a whirling, "jump rope" like motion. We identify nondimensional gate voltage, resonator geometry, quality factor, and flexural and axial elastic stiffnesses for which such motions can arise. The deliberate use of nonlinear and nonplanar motions opens up a variety of new modalities for this class of nanoelectromechanical systems that are not accessible in the linear operating regime.     

Additive soft-lithographic patterning of submicrometer- and nanometer-scale large-area resists on electronic materials

We describe a novel soft-lithographic technique possessing broad utility for the fabrication of large area, nanoscale ( approximately 100 nm) multilayer resist structures on electronic material substrates. This additive patterning method transfers ultrathin poly(dimethylsiloxane) (PDMS) decals to an underlying SiO(2)-capped organic planarazation layer. The PDMS patterns serve as a latent image through which high-quality multilayer resist structures can be developed using reactive ion-beam etching.     

Nanometer patterning with ice

Nanostructures can be patterned with focused electron or ion beams in thin, stable, conformal films of water ice grown on silicon. We use these patterns to reliably fabricate sub-20 nm wide metal lines and exceptionally well-defined, sub-10 nanometer beam-induced chemical surface transformations. We argue more generally that solid-phase condensed gases of low sublimation energy are ideal materials for nanoscale patterning, and water, quite remarkably, may be among the most useful.     

Nanopatterning of diamond films with composite oxide mask of metal octylates in electron beam lithography

The fabrication of diamond nanopatterns by electron cyclotron resonance (ECR) oxygen plasma with a composite metal octylate mask was investigated using electron beam lithography technology. A high etching selectivity of 14 was obtained with Bi₄Ti₃O₁₂ octylate film as a mask under the plasma-etching conditions of microwave power of 300 W and oxygen gas flow rate of 3 sccm. The metal naphthenates and metal octylates exhibited negative exposure characteristics. The sensitivity of metal naphthenates (1.2×10^–3 C cm^–2) was ten times lower than that of polymethyl methacrylate (PMMA) resist, while that of octylates (8.0×10^–5 C cm^–2) was in good agreement with that of PMMA resist (6.0×10^–5 C cm^–2). The resulting minimum chemical vapor deposited (CVD) diamond line-width of 100 nm with a height of approximately 1 m was fabricated with a Bi₄Ti₃O₁₂ octylate mask.