Quantum simulation for peak broadening in atom lithography

A grating structure with period of half of the laser wavelength generated by focusing Cr atoms with nearly resonant laser standing wave atom lens was simulated using a quantum-mechanical model.     

Structure formation in atom lithography using geometric collimation

Atom lithography uses standing wave light fields as arrays of lenses to focus neutral atom beams into line patterns on a substrate. Laser cooled atom beams are commonly used, but an atom beam source with a small opening placed at a large distance from a substrate creates atom beams which are locally geometrically collimated on the substrate. These beams have local offset angles with respect to the substrate. We show that this affects the height, width, shape, and position of the created structures. We find that simulated effects are partially obscured in experiments by substrate-dependent diffusion of atoms, while scattering and interference just above the substrate limit the quality of the standing wave lens. We find that in atom lithography without laser cooling the atom beam source geometry is imaged onto the substrate by the standing wave lens. We therefore propose using structured atom beam sources to image more complex patterns on subwavelength scales in a massively parallel way.     

一种可用于原子全息光刻的二元计算全息新方法

 原子全息光刻即采用二元计算全息片掩模来操纵原子,实现微细结构的制作。传统二元计算全息产生的全息片在重现时会产生不止一个实像,这对于原子全息光刻的操作是不利的。提出了一种非相位编码的方法,该方法利用基元函数叠加方式产生实的编码前全息图,再利用类似罗曼Ⅲ型的编码方式产生二元计算全息图。模拟结果表明,利用该方法产生的掩模板可以产生单一的同原始图案相对应的微细结构。     

一种可用于原子全息光刻的二元计算全息新方法

原子全息光刻即采用二元计算全息片掩模来操纵原子,实现微细结构的制作。传统二元计算全息产生的全息片在重现时会产生不止一个实像,这对于原子全息光刻的操作是不利的。提出了一种非相位编码的方法,该方法利用基元函数叠加方式产生实的编码前全息图,再利用类似罗曼Ⅲ型的编码方式产生二元计算全息图。模拟结果表明,利用该方法产生的掩模板可以产生单一的同原始图案相对应的微细结构。     

Classical simulation of atomic beam focusing and deposition for atom lithography

We start from the intensity distribution of a standing wave (SW) laser field and deduce the classical equation of atomic motion. The image distortion is analyzed using transfer function approach. Atomic flux density distribution as a function of propagation distance is calculated based on Monte-Carlo scheme and trajectory tracing method. Simulation results have shown that source imperfection, especially beam spread, plays an important role in broadening the feature width, and the focus depth of atom lens for real atomic source is longer than that for perfect source. The ideal focal plane can be easily determined by the variation of atomic density at the minimal potential of the laser field as a function of traveling distance.     

Efficient generation of cold atoms towards a source for atom lithography

We report on the efficient generation of cold rubidium atoms as a potential coherent atom source for atom lithography. We successfully trapped and cooled 2.6 × 10⁸ atoms in 5 s with a conventional magneto-optical trap simply by enlarging the diameter of the laser beam to 20 mm. The size of the laser-cooled atom cloud was measured to be 10 × 7 × 7 mm³. The number of trapped atoms was approximately 10 times as large as that of previous typical results, while the loading time of atoms remained the same.     

Diffusion of group III and V elements in SiO2

The diffusion of Group III and V elements in SiO₂ will be reviewed. These elements exhibit specific diffusion properties related to the chemical state in which they are incorporated in SiO₂. The occurrence of these chemical states depends on the conditions under which they are incorporated in SiO₂. Ion implantation of III and V elements results in a situation in which the oxide network is deficient in oxygen. This can lead to incorporation of the implanted element in a specific chemical state. Group III and V elements can be incorporated into SiO₂ in three configurations: One in their high valence state (III or V respectively) and two with their low valence state (I or III respectively), depending on thermodynamical stability and on the composition of the ambient gas. The mobility of III and V elements is influenced by other elements which often are supplied from the ambient. A summary will be presented of the more recent diffusion data, including the differences due to different chemical states, ambient effects and concentration dependent diffusion.     

Fragmentation of dodecanethiol molecules: application to self-assembled monolayer damage in atom lithography

Atom lithography commonly employs self-assem- bled monolayers (SAMs) of alkanethiols which act as resists to protect prepared surfaces. Metastable atomic species such as helium are used to damage the resist, enabling pattern transfer via mask lithography, followed by wet chemical etching. The damage mechanism is, however, not well understood. Here we report studies of fragmentation of dodecanethiol (DDT) molecules embedded in helium nano-droplets that have been irradiated by an electron beam. The results of the charge-transfer fragmentation process provide the first experimental data on the damage mechanisms that occur in the metastable helium/SAM interaction. Received: 20 September 1999 / Revised version: 6 December 1999 / Published online: 8 March 2000     

Structured mirror array for two-dimensional collimation of a chromium beam in atom lithography

Direct-write atom lithography,one of the potential nanofabrication techniques,is restricted by some difficulties in producing optical masks for the deposition of complex structures.In order to make further progress,a structured mirror array is developed to transversely collimate the chromium atomic beam in two dimensions.The best collimation is obtained when the laser red detunes by natural line-width of transition 7S3 → 7P40 of the chromium atom.The collimation ratio is 0.45 vertically(in x axis),and it is 0.55 horizontally(in y axis).The theoretical model is also simulated,and success of our structured mirror array is achieved.     

氢原子基下径向矩阵元的递推关系

推导出氢原子基下径向矩阵元〈nl|rk|n′l′〉所满足的递推关系.     

Magnetic ordering in molybdenum sulphides alloyed with third group elements

Molybdenum sulphides alloyed with gallium and aluminium show magnetic ordering at low temperatures. This is proposed to explain the interesting features of the superconductor Mo₅SnGa_0.5S₆.     

Singlet excited states of anions with higher main group elements

Previous studies have shown that dipole-bound excited states exist for certain small anions. However, valence excited states have been reported for some closed-shell anions, but those with singlet valence excited states have, thus far, contained a single silicon atom. This work uses high-level coupled cluster theory previously shown to reproduce excited state energies to better than 0.1 eV compared with experiment in order to examine the electronic excited state properties of anions containing silicon and other higher main group atoms as well as their first row analogues. Of the 14 anions involved in this study, 9 possess bound excited states of some kind: CH₂SN^?, C₃H^?, CCSiH^?, CCSH^?, CCNH^?₂, CCPH^?₂, BH₃PH^?₂, AlH₃NH^?₂ and AlH₃PH^?₂. Two possess clear valence states: CCSiH^? and its first row analogue C₃H^?. Substantial mixing appears to be present in the valence and dipole-bound characters for the first excited state wavefunctions of many of the systems reporting excited states, but the mixing is most pronounced with the ammonia borane-like AlH₃NH^?₂, and AlH₃PH^?₂ anions. Inclusion of second row atoms in anions whose corresponding radical is strongly dipolar increases the likelihood for the existence of excited states of any kind, but among the systems considered to date with this methodology, only the nature of group 14 atoms in small, closed-shell anions has yet been shown to allow valence singlet excited states.     

On the possibility of applying kinoform elements in mirror projectors for EUV lithography

The potential of the technology of reflective diffraction (holographic) optical elements intended for the EUV range is considered, and their application in projection lithography is discussed.     

Positronium atom reactions in aqueous solutions of iron III complexes

The rate constants for the reactions between thermal Ps atoms and a series of iron (III) compounds including some complexes which can be considered as model compounds for biologically active systems have been determined. Paper E2 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973).     

Quantum lithography with classical light

We show how to achieve subwavelength diffraction and imaging with classical light, previously thought to require quantum fields. By correlating wave vector and frequency in a narrow band, multiphoton detection process that uses Doppleron-type resonances, we show how to achieve arbitrary focal and image plane patterning with classical laser light at submultiples of the Rayleigh limit, with high efficiency, visibility, and spatial coherence. A frequency-selective measurement process thus allows one to simulate, semiclassically, the path-number correlations that distinguish a quantum entangled field.     

Atom lithography with ytterbium beam

We successfully produced periodic ytterbium (Yb) narrow lines on a substrate using near-resonant laser light and the direct-write atom-lithography technique. The Yb atom is a promising material for nanofabrication using atom optics due to its electrical conductivity, the laser wavelength required for handling the atoms, the vapor pressure of the fabrication process, etc. The ¹⁷⁴Yb atoms collimated by Doppler cooling were channeled by the dipole force of an optical standing wave and then deposited onto a substrate. We clearly observed a grating pattern of Yb atoms fabricated on the substrate with a line separation of approximately 200 nm after examining the surface of the substrate with atomic force microscope. This is the first demonstration of nanofabrication using the atom-optical approach with Yb atoms. PACS 32.80.-t; 32.80.-Pj     

X-ray lithography with synchrotron radiation

Manufactures of silicon integrated circuits increasingly rely on high resolution, high throughput, and litography techniques based on parallel mask projection. The once simple technique of projecting an image of a mask on a wafer, however, is now being replaced by more elaborate systems at an ever faster rate. Of the possible successors to photolithography in the production of structures smaller than 0.7 m, the most promising appears to be X-ray litography with synchrotron radiation. The development problems of this new technique are related to the mask technology, alignment systems, resist materials, and compact, low-cost storage rings.