Atomic level deposition to extend Moore’s law and beyond

In the past decades,Moore’s law drives the semiconductor industry to continuously shrink the critical size of transistors down to 7 nm.As transistors further downscaling to smaller sizes,the law reaches its limitation,and the increase of transistors density on the chip decelerates.Up to now,extreme ultraviolet lithography has been used in some key steps,and it is facing alignment precision and high costs for high-volume manufacturing.Meanwhile,the introduction of new materials and 3D complex structures brings serious challenges for top-down methods.Thus,bottom-up schemes are believed to be necessary methods combined with the top-down processes.In this article,atomic level deposition methods are reviewed and categorized to extend Moore’s law and beyond.Firstly,the deposition brings lateral angstrom resolution to the vertical direction as well as top-down etching,such as double patterning,transfer of nanowires,deposition of nanotubes,and so on.Secondly,various template-assisted selective deposition methods including dielectric templates,inhibitors and correction steps have been utilized for the alignment of 3D complex structures.Higher resolution can be achieved by inherently selective deposition,and the underlying selective mechanism is discussed.Finally,the requirements for higher precision and efficiency manufacturing are also discussed,including the equipment,integration processes,scale-up issues,etc.The article reviews low dimensional manufacturing and integration of 3D complex structures for the extension of Moore’s law in semiconductor fields,and emerging fields including but not limited to energy,catalysis,sensor and biomedicals.

Higher-Order Squeezing for Atomic Dipole of a Three-Level Atom in the Kerr-Like Medium Cavity Fields

In this paper, evolution of the higher order squeezing for atomic dipole of three level atom in the Kerr like medium is investigated. The atom discussed has two configurations and is driven by the single mode coherent state field. Our results show that the squeezing effects are clearly influenced by nonlinear parameters, the initial atom state and the detuning.

Bottom-up design and assembly with superatomic building blocks

Constructing specific structures from the bottom up with artificial units is an important interdisciplinary topic involving physics,chemistry,materials,and so on.In this work,we theoretically demonstrated the feasibility of using superatoms as building blocks to assemble a complex at atomic-level precision.By using a series of actinide-based endohedral metallofullerene(EMF)superatoms that can form one,two,three and four chemical bonds,a planar complex with intra-and inter-molecular interactions was assembled on the Au(111)surface.This complex is composed of two parts,containing ten and eight superatoms,respectively.The electronic structure analysis shows that the electron density inside each part is connected and the closed-shell electronic arrangement system is designed.There is also an obvious van der Waals boundary by physical adsorption between the two parts,and a stable complex is formed.Since this complex is realized by the first-principles calculations of quantum mechanics,our results help not only achieve atomic-level precision construction with artificial superatomic units but also maintain atomic-level functional properties.

The Quantum Condition That Should Have Been Assumed by Bohr When Deriving the Energy Levels of a Hydrogen Atom

Bohr assumed a quantum condition when deriving the energy levels of a hydrogen atom. This famous quantum condition was not derived logically, but it beautifully explained the energy levels of the hydrogen atom. Therefore, Bohr’s quantum condition was accepted by physicists. However, the energy levels predicted by the eventually completed quantum mechanics do not match perfectly with the predictions of Bohr. For this reason, it cannot be said that Bohr’s quantum condition is a perfectly correct assumption. Since the mass of an electron which moves inside a hydrogen atom varies, Bohr’s quantum condition must be revised. However, the newly derived relativistic quantum condition is too complex to be assumed at the beginning. The velocity of an electron in a hydrogen atom is known as the Bohr velocity. This velocity can be derived from the formula for energy levels derived by Bohr. The velocity v of an electron including the principal quantum number n is given by αc/n. This paper elucidates the fact that this formula is built into Bohr’s quantum condition. It is also concluded in this paper that it is precisely this velocity formula that is the quantum condition that should have been assumed in the first place by Bohr. From Bohr’s quantum condition, it is impossible to derive the relativistic energy levels of a hydrogen atom, but they can be derived from the new quantum condition. This paper proposes raising the status of the previously-known Bohr velocity formula.

The Pancharatnam Phase of a Three-Level Atom Coupled to Two Systems of N-Two Level Atoms

In this paper, we present the analytical solution for the model that describes the interaction between a three-level atom and two systems of N-two level atoms. The effects of the quantum numbers and the coupling parameters between spins on the Pancharatnam phase and the atomic inversion, for some special cases of the initial states, are investigated. The comparison between the two effects shows that the analytic results are well consistent.

Bohr’s Spectrum of Quantum States in the Atomic Hydrogen Deduced from the Uncertainty Principle for Energy and Time

A modified uncertainty principle coupling the intervals of energy and time can lead to the shortest distance attained in course of the excitation process, as well as the shortest possible time interval for that process. These lower bounds are much similar to the interval limits deduced on both the experimental and theoretical footing in the era when the Heisenberg uncertainty principle has been developed. In effect of the bounds existence, a maximal nuclear charge Ze acceptable for the Bohr atomic ion could be calculated. In the next step the velocity of electron transitions between the Bohr orbits is found to be close to the speed of light. This result provides us with the energy spectrum of transitions similar to that obtained in the Bohr’s model. A momentary force acting on the electrons in course of their transitions is estimated to be by many orders larger than a steady electrostatic force existent between the atomic electron and the nucleus.

Visible-Light-Driven Methane Conversion with Oxygen Enabled by Atomically Precise Nickel Catalyst

It remains an extreme challenge to activate thermodynamically unfavorable,chemically inert methane molecules under mild conditions.Herein,we report a molecular-like nickel-thiolate hexameric cluster[Ni_(6)(PET)_(12);PET=SC_(2)H_(4)Ph]catalyst that resembles a double crown,comprising of a hexagonal Ni6 kernel encapsulated by an exterior shell of 12 thiolates capable of efficient conversion of methane plus O_(2) to methanol and formic acid under visible light irradiation.

Atom elimination strategy for MoS_(2) nanosheets to enhance photocatalytic hydrogen evolution

The regulation of the basic properties of atom-economic catalysts at the atomic scale and atomic-level insights into the underlying mechanism of catalysis are less explored. We engineer the surface of vertical immobilized MoS_(2) on dispersible TiO_(2) nanofibers via atomic subtraction to precisely manipulate active sites at the atomic level. The photocatalytic performances of TiO_(2) @MoS_(2) after H_(2) reduction towards the hydrogen production under visible light irradiation(>420 nm) are about 4 times that of TiO_(2) @MoS_(2) before H_(2) reduction. Importantly, the enhanced stability of TiO_(2) @MoS_(2) lasts for at least 30 h. Promising catalytic activity that is attributed to omnidirectional exposed active sites located defects, edges, corners that are transformed from the subtractive atomic sites could be exhumed comprehensively. This work will provide an intriguing and effective approach on tuning electronic structures for optimizing the catalytic activity at the atomic level by atom elimination strategy. To get rid of a few atomics on the surface of atomically-thin MoS_(2) nanosheet could be a prudent avenue for enabling the basal plane of MoS_(2) catalytically active.

Mandrel degradation model of combined fast and slow processes

In this paper, we report the study of degradation for a kind of ideal mandrel material called poly-α-methylstyrene based on theoretical and experimental methods. First-principles calculations reveal two types of process: depolymerization and hydrogen-transfer-induced chain scission. The energy barrier for the former(0.68–0.82 eV) is smaller than that for most of the latter(1.39–4.23 eV). More importantly, reaction rates suggest that the former is fast whereas the latter is mostly slow, which can result in a difference of 5–31 orders of magnitude at 550 K. Furthermore, a thermogravimetric experiment shows that the activation energy of 2.53 eV for degradation is between those of fast and slow processes,corresponding to the theoretical average value of multiple reaction paths. Thus, a mandrel degradation model combining fast and slow processes is established at the atomic level. Our work provides a direction for research into the key technology of target fabrication in inertial confinement fusion.

Electrostatic Interactions in Protein Molecules:A Novel Model for the Calculation of the Intrinsic pKa of Lysozyme

A Monte Carlo simulation method was developed for atomic level calculation of the solvent accessible surface(SAS) area of a protein. As an example, the accessibility value of each atom, as well as all the residues of lysozyme was calculated using this method. The calculated accessibility values were applied to the prediction of intrinsic pK a volumes of Asp52 and Glu35, two embedded residues in the active site of lysozyme. In previous methods, the two active site residues were treated as an entity in calculating the overall free electrostatic energy, with results showing great deviation from the experimental data. With atomic level observation, we revealed that each of these two residues has an exposed ionic atom. A more satisfactory result was obtained by taking this into account. A calculated titration curve closer to the experimental one was obtained by using these more accurately calculated pK a value. Results indicated that individual atoms on embedded residues contributed significantly to overall electrostatic properties.