Epitaxy: the motion picture

The engineering of many modern electronic devices demands control over a crystal down to the thickness of a single layer of atoms—and future demands will be even more challenging. Such control is achieved by the method of crystal growth known as epitaxy, and that makes this method the subject of intense study. More than that, recent advances are revolutionizing our knowledge of how surfaces grow. In fact, growing surfaces show a beautifully rich variety of phenomena, many of which are only now beginning to be uncovered. In the past few years many surface imaging techniques have been used to give us a close look at how crystals grow—while they are growing. The purpose of this article will be to illustrate some of the ways real surfaces grow and change as revealed by some of the latest in situ microscopic imaging technologies.

It is often said that crystal growth is more of an art than a science. Here we will show that it is emphatically both.     

Dissipation: the phase-space perspective

We show, through a refinement of the work theorem, that the average dissipation, upon perturbing a Hamiltonian system arbitrarily far out of equilibrium in a transition between two canonical equilibrium states, is exactly given by =W-DeltaF=kTD(rho||rho[over ])=kT, where rho and rho[over ] are the phase-space density of the system measured at the same intermediate but otherwise arbitrary point in time, for the forward and backward process. D(rho||rho[over ]) is the relative entropy of rho versus rho[over ]. This result also implies general inequalities, which are significantly more accurate than the second law and include, as a special case, the celebrated Landauer principle on the dissipation involved in irreversible computations.     

Gravity: the inside story

It is well known that one could determine the kinematics of gravity by using the Principle of Equivalence and local inertial frames. I describe how the dynamics of gravity can be similarly understood by suitable thought experiments in a local Rindler frame. This approach puts in proper context several unexplained features of gravity and describes the dynamics of spacetime in a broader setting than in Einstein’s theory. First Award in the 2008 Essay Competition of the Gravity Research Foundation.     

Optical interconnects: the challenge

As the integrated circuit complexity and speed increase, interconnects become the main bottleneck in microelectronics processes for further improvements of the performances. Optics is considered as a possible alternative solution to meet the expected requirements, and has already proven its advantages for distances which progressively shorten from optical telecommunications towards inter-boards, and then interchip connections. This paper focuses on the potentialities of optical solutions for intrachip interconnects.     

Conventional interconnects: the crisis

As the design rules drop below 200 nm, a variety of problems emerges such as RC delay, electromigration resistance and heat dissipation exacerbated by increasing chip power. The use of Copper should solve resistivity and electromigration problems but reliability issue with respect to an efficient diffusion barrier is a concern. Low- k dielectrics allowing capacitance reduction have low thermal conductivity thus poor heat dissipation capability. Integration of Copper and low- k dielectrics is intensively studied world wide. The following gives an overview of the international state of the art to overcome critical issues of advanced interconnects.     

CMB: the isotropic part

The Cosmic Microwave Background, or CMB, is the only truly diffuse background, whereas the other backgrounds come from the integrated light (along the line of sight) of various sources. The CMB is now known, thanks to the FIRAS experiment above the COBE satellite, to have a nearly perfect blackbody spectrum. This proves to be quite constraining on early energy releases. We review the average spectrum of the CMB with respect to other backgrounds and the consequences regarding the history of the early Universe. To cite this article: F.R. Bouchet, J.-L. Puget, C. R. Physique 4 (2003).     

Aquarian Comets: the Origin of the Oceans

When comets such as Hale-Bopp pass close to the Eath they bring clues to the origins of the solar system; and like all great travellers they tell stories of lost world before heading off again to distant much more than tales. They might have brought the right conditions for the origine of life itselfIn an edited version of a talk given at Uppsala university, Sweden in May Hans Rickman describes how comets might have brought the oceans from distant parts of the solar system and, opposite, a brief report of the lateston the theory     

On the origin of the visible emission in KBr:Tl and KCl:Tl crystals

The intensity of the visible emission of KBr:Tl at 440 nm is shown to increase linearly with the absorption in the A₁ band at 4.64 eV (267 nm). The latter band increased with the square of the Tl⁺ ions concentration, which supports its assignment to thallium dimers. Similarities in behavior between the 440 nm emission of KBr:Tl and the 475 nm emission of KCl:Tl suggest that the latter is also related to dimers. This is supported by the superlinear dependence of this emission on the Tl⁺ ion concentration. Deviations ofthe superlinearity from the square dependence expected for dimers is explained by the overlap between the weak dimer absorption and the very strong A-band.The 440 nm emission of KBr:Tl was found to be excited only in the A₁ component of the dimer absorption and not in the stronger A₂ component. This indicates that the emission process may be compound.