Four-layer Films Research Articles

Laser induced mixing and microstructures in GeAl thin multilayer films

A study of the laser mixing of four-layered thin films of Ge/Al has been made. We combine Rutherford backscattering (RBS) and transmission electron microscopy (TEM) to perform depth profile and microstructure analysis. The results show that the mixing is interfacially initiated and that the surface layer (Ge) and the layer at the film-substrate interface (Al) remain partially unmixed. The degree of mixing does not depend critically on the as-grown layer configuration but does depend on the nature of the substrate. The mixing process is well simulated in the frame of the classical diffusion theory and the estimated average temperatures are close to that of the eutectic. The mixed layer is found to be amorphous and the calculated cooling rates are in the 109 Ks−1 range.

Heat-capacity anomaly from four-layer liquid-crystal films.

A high-sensitivity ac calorimeter system has been developed to investigate the temperature variation of the heat capacity from free-standing liquid-crystal films. We have observed a clear evolution of the heat-capacity anomaly from films of the liquid-crystal compound 650 BC as the films are reduced in thickness from 10 to 4 molecular layers near their bulk smectic-A--hexatic-B transition. Here 650BC refers to n-hexyl-4'-n-pentyloxybiphenyl-4-carboxylate. The four-layer films show a single, sharp, and cusplike heat-capacity peak without thermal hysteresis.

Thermal Property Evolution Toward Effectively Two-Dimensional Substrate-Free Systems

ABSTRACTA high-resolution differential quasi-adiabatic calorimeter has been developed to investigate the physical properties of freestanding liquid-crystal films. Our recent heat-capacity studies near the smectic-A-hexatic-B transition of both 65OBC and 46OBC freestanding films clearly demonstrate the evolution towards twodimensional limiting behavior in four-layer films. As the film thickness decreases towards four molecular layers, the heatcapacity anomalies first display separate peaks for the surface and interior transitions and then evolve to one dominated by the surface transition.

Pseudofunction method: Application to a monolayer of CO and to the Si(111) surface.

The newly developed pseudofunction method has been developed to provide ab initio energy bands and binding-energy curves for molecules, surfaces, and bulk. The effectiveness of this approach is demonstrated by computing the electronic properties of a CO molecule in a monolayer configuration. We find the CO bond length, dipole moment derivative, and the vibrational frequency are close to that of a free CO molecule. We have further demonstrated this new method by computing the surface relaxation of a Si(111)(1\ifmmode\times\else\texttimes\fi{}1) four-layer film with one surface saturated by H. The unsaturated surface relaxes inwards by 0.086 A\r{} with a vibrational excitation of 0.038 eV, nearly identical to generalized-valence-bond cluster calculations.

Entropy of thin solid layers

The entropies of thin adsorbed solid layers and of three-dimensional solid are compared for a model of harmonic nearest-neighbor adatom coupling and harmonic first layer coupling to the substrate. The competing effects of the constraining substrate coupling and of geometry are illustrated for one-layer to four-layer films. The entropy difference at layer condensation relative to the three-dimensional solid is calculated: the values for monolayer condensation are at the lower end of the range of values derived from experiment; the values at further layer condensations are much smaller than many experimental values.

Recording Characteristics of Magneto-Optical Disk with Quadrilayer Structure

The effects of recording sensitivity and recording conditions on bits recorded on sputtered four-layer GdTbFe film are reported. A correlation was seen between recorded bit length and film optical absorption per unit thickness. As films were made thinner, the resulting bit length grew longer and the film became more sensitive. Fluctuation in bit widths was minimum at a recording power of 5.1 mW and a bias field strength of 500 to 600 Oe. The bit size was determined by the film temperature and coercive force, the bias field, and the temperature gradient in the medium. For 4/5 modulation, the shortest bit length was approximately 1.3 μm.

Improvement of NDRO characteristics of fine-striped magnetic thin film memory element

This paper reports the improvements of the NDRO characteristics in the FSM element achieved with combined application of multilayer film technology and topography control, and an improved process in forming the closed flux path structure. To form the adaptable closed flux path structure the following multistep procedure was developed: 1) deposition of magnetic film on the insulating surface; 2) deposition of Cu stripes over the film; 3) further deposition of magnetic fdm; and 4) removal of magnetic film between stripes by photoetching to form independent digit stripes. This improved method ensures a complete closed flux path between the magnetic films at the bottom and top. Thus, uniform memory characteristics and reproducibility are achieved. The bottom magnetic film is a four-layer film composed of Ni-Fe and Ni-Co films. On this film, Cu stripes, 2 μm thick and 100 μm wide, are deposited. Furthermore, a Ni-Fe film, 1 μm thick, is deposited. Nodules, 1-1.5 μm in diameter, formed on the Cu stripes by controlling deposition conditions, provide the top magnetic film with NDRO characteristics through the topography effect. The sense signal at 4 mV output from two intersections per bit is obtained with a word current at 150 mA having a rise time of 25ns.

Disturb properties of exchange-coupled composite plated wires

Disturb properties of four-layered films of Permalloy and Co-Ni alternately electroplated onto 0.1-mm diameter wires are reported. NDRO behaviors with various kinds of disturbs are shown. It is found that word disturbs intervening between digit disturbs are very influential. The mechanism in this case is different from that of wall creeping previously reported. Static changes of magnetization or hysteresis by intervening word pulses play an important role in the former case, although in the latter case dynamic changes of magnetization do. Some strange disturb behaviors are also found. These composite films have a wide operating region for NDRO.

Multiple Beam Interferometric Study of `Built-up' Films of Barium Stearate

A direct determination of the metrical thickness of mono- and multi-molecular films of barium stearate has been carried out with the use of multiple beam interferometry. The thickness of the unimolecular film, as obtained from measurements on a four-layer film, is 25.7 ± 0.3 A which is in excellent agreement with the length of the molecular chain of barium stearate (=25.75 ± 0.25 A) as obtained from Fankuchen's X-ray data. The technique employed eliminates differential phase change effects and does not involve the refractive index of the films. The result confirms the monomolecular spreading of stearic acid on a water surface.