A. G. Schrott

MOTT TRANSITION FIELD EFFECT TRANSISTOR

A field effect transistor fabricated with an oxide channel has been shown to demonstrate switching characteristics similar to conventional siliconmetal oxide field effect transistors. This device is believed to operate via a Mott metal-insulator transition induced by the gate field, and offers a potential technology alternative for the regime beyond silicon scaling limitations.

Enhanced Cu‐Teflon adhesion by presputtering prior to the Cu deposition

Adhesion of Cu to Teflon has been studied by depositing Cu to Teflon with and without a presputtering prior to the Cu deposition. Without presputtering, a weak adhesion is observed, with a value of 1 g/mm, which fails the scotch tape test. With a presputtering using 500 eV Ar+ ions, the adhesion rapidly increases, becoming evident after a sputtering of 10 s, and reaches maximal increases of 50 times at longer sputtering times. All the Cu films deposited after presputtering show strong adhesion, and can only be removed by forceful scratching with sharp tools. The presputtering was shown to change both the surface morphology of Teflon, with the deposited Cu following the morphologies created, and the interface chemical bonding between Cu and Teflon as revealed by x‐ray photoelectron spectroscopy. Exposure of the presputtered Teflon to air prior to the Cu deposition shows no effect on the strong adhesion obtained. An interface bonding model is suggested for the enhanced adhesion observed.

Laser‐Assisted Seeding for Electroless Plating on Polyimide Surfaces

Excimer laser pulses with wavelengths of 248 and 308 nm were used to selectively seed Pd on polyimide (PI) surfaces, making them suitable for electroless plating. This novel seeding process for insulating materials is accomplished with the sample immersed in the seeding solution, occurs only on the areas of the substrate that are illuminated (through the liquid) by the laser light, and does not require prior treatment of the surface. The seeding solution is transparent to the laser light and the metal deposition occurs as a consequence of the photoabsorption in the solid. This leads to electron transfer from the solid film into the solution and reduction of the Pd ions in contact with the surface. The Pd content of the seeded samples increased with the number of pulses, but was independent of repetition rate. The deposition rate of Pd did not exhibit a significant dependence on wavelength, in agreement with UV absorption spectra of PI and a single photon absorption process for electron excitation to allowed unoccupied states. As for the PD distribution, the deposits consisted of islands with distributions that depended on surface properties as well as on laser-material interactions. Sufficient PD seeds for uniform electroless plating of Cu and Co were attained after 3000 pulses at fluences ≃30 mJ/cm 2 . Although these fluences are much lower than those used for ablation of PI under water, distinct kinds of surface roughness were observed depending on the laser light and on the different types of PI

Ferroelectric field-effect transistor with a SrRuxTi1−xO3 channel

A ferroelectric field-effect transistor with a SrRuxTi1−xO3 solid-solution channel layer and a lead zirconate titanate gate oxide has been fabricated. The remnant polarization of the ferroelectric yields two states at 0 V, which produce a relative change in channel resistance (ΔR/R) of 75% and a coercivity of 3 V. The channel has sufficient off-state free carrier concentration to provide sufficient balancing charge for ferroelectric stability. The device was subjected to more than 1010 read-write cycles with no degradation. This nonvolatile device offers the possibility of a nondestructive, current sense memory cell with good retention properties.

A-site surface termination in strontium titanate single crystals

It is well known that chemical etching of strontium titanate (SrTiO3) results in titanium-terminated (B site) surfaces. In this letter, we describe a facile method for generating strontium-terminated surfaces in SrTiO3. We demonstrate that a substrate treatment consisting of a low-power oxygen ashing followed by annealing yields a strontium (A site)-terminated surface in single-crystal SrTiO3 (100). This surface termination of the substrate allows the deposition of cuprate films with improved quality.

Room-temperature oxide field-effect transistor with buried channel

In this letter, we introduce an architecture for a room-temperature oxide channel field-effect transistor where the oxide channel material is buried below the gate oxide layer. This architecture has several significant advantages over the surface channel architecture [D. M. Newns, J. A. Misewich, C. C. Tseui, A. Gupta, B. A. Scott, and A. Schrott, Appl. Phys. Lett. 73, 780 (1998).] in coupling capacitance, channel mobility, and channel stability. Although the transconductance in the devices has been improved to 45 μS (at Vd=1 V and Vg=2 V for a channel length of 1 μm and width=150 μm), capacitance measurements show that the surface charge density is still below the optimal theoretical value.

X‐Ray Absorption Study of Electrochemically Grown Oxide Films on AlCr Sputtered Alloys II . In Situ Studies

Research was carried out in part at the National Synchroton Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. A. J. D. and H. S. I. were supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016.

In Situ X‐Ray Absorption Study of Chromium Valency Changes in Passive Oxides on Sputtered AlCr Thin Films under Electrochemical Control

This work was carried out in part under the auspices of the US Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016. XANES measurements were carried out at the National Synchrotron Light Source Beamline X19A.

Corrosion inhibition of cobalt with a thin film of Cu-BTA

Electrochemical techniques, ellipsometry and X-ray photoelectron spectroscopy were used to evaluate the use of benzotriazole, alone or in combination with boric acid/borate buffer and dilute copper sulfate for the protection of cobalt. The data indicate that in slightly alkaline solutions benzotriazole is a strong inhibitor for cobalt corrosion, whereas in water and neutral solutions it produces a barely measurable effect. In the presence of benzotriazole and Cu[sup +2] ions, spontaneous reduction of copper ions leads to the formation of a thin film of Cu-BTA on the cobalt surface. This film acts as a corrosion protector that is better than benzotriazole, with a significant reduction of the corrosion rate even during subsequent exposure to solutions without inhibitors.

Corrosion and Passivation of Fe and FeN Films

The role of nitrogen in corrosion and passivation of thin Fe-N films was studied. Sputtered films with different levels of nitrogen were characterized for composition, conductivity, stress, and crystallinity. Corrosion and passivation of the films were evaluated by electrochemical measurements combined with in situ ellipsometry and ex situ x-ray photoelectron spectroscopy. The results indicate that in deaerated solutions the primary action of N is to reduce the catalytic activity of the surface for the hydrogen reaction and thereby reduce corrosion. In aerated solutions the corrosion rate increases with N content. Kinetics of the protective oxide formation as a function of potential, percent N, and the presence of borate buffer are discussed in detail. The work is relevant to the behavior of oxide-free Fe-N surfaces in contact with mild, nearly neutral electrolytes, such as could be used in fabrication of magnetic recording heads.