In fabricating a thin film transistor, an active layer comprising a silicon semiconductor is formed on a substrate having an insulating surface Hydrogen is introduced into The active layer A thin film comprising SiO x N y is formed to cover the active layer and then a gate insulating film comprising a silicon oxide film formed on the thin film comprising SiO x N y  Also, a thin film comprising SiO x N y is formed under the active layer The active layer includes a metal element at a concentration of 1×10 15 to 1×10 19 cm −3 and hydrogen at a concentration of 2×10 19 to 5×10 21 cm −3 

Semiconductor device and method for forming the same

Using Rutherford backscattering technique, we have measured the angular distribution of the composition and thickness of the Y‐Ba‐Cu oxide film deposited by firing excimer laser (30 ns, 248 nm) pulses at a stoichiometric Y1Ba2Cu3O7−x pellet. The angular distribution consisted of two distinct components: one a cos θ component, a result of evaporation, and the other a highly forward directed component, a result of a secondary ejection process. The evaporated component is nonstoichiometric, as one would expect, whereas the forward‐directed component has a composition close to that of the pellet. Further, the forward‐directed stoichiometric component increases with the laser energy density in comparison with the evaporated component. These observations are discussed in the context of current models of laser‐induced material ejection at surfaces.The laser energy dependence of the deposition is of critical importance in controlling the film stoichiometry.

Observation of two distinct components during pulsed laser deposition of high Tc superconducting films

Superconducting thin films of Y‐Ba‐Cu oxide have been prepared on yttria‐stabilized zirconia substrates using metal trifluoroacetate spin‐on precursors. The films exhibit an extremely sharp resistive transition with zero resistance at temperatures as high as 94 K. The superconducting phase is formed by a three‐step process: (a) decomposition of the spun‐on trifluoroacetate film to the fluorides, (b) conversion of the fluorides to oxides by reacting with water vapor, and (c) annealing followed by slow cooling in oxygen. The properties of the films depend on the amount of conversion of the fluorides by reaction with water. Films which show the presence of some unreacted barium fluoride have strong c‐axis normal preferred orientation, with a sharp resistive transition. When all the barium fluoride is converted, the film is more randomly oriented and exhibits a broader transition to zero resistance.

Superconducting oxide films with high transition temperature prepared from metal trifluoroacetate precursors

We have developed a new way of making grain boundary junctions in YBa2Cu3O7 thin films by controlling the in‐plane epitaxy of the deposited film using seed and buffer layers. We produce 45° grain boundaries along photolithographically defined lines. The typical value of the critical current density of the junctions is 103–104 A/cm2 at 4.2 K and 102–103 A/cm2 at 77 K, while the rest of the film has a critical current density of 1–3×106 A/cm2 at 77 K. The current‐voltage characteristics of the junctions show resistively shunted junction behavior and we have used them to fabricate dc superconducting quantum interference devices (SQUIDs) which show modulation at temperatures well above 77 K. This is the first planar high Tc Josephson junction technology that appears readily extendable to high Tc integrated circuits.

Bi‐epitaxial grain boundary junctions in YBa2Cu3O7

Large-area, uniform, high critical current density (Jc) YBa2Cu3O7−x (YBCO) superconductor films are now routinely obtained by metalorganic deposition using trifluoroacetates (TFA-MOD) This method does not require any expensive vacuum apparatus at any time during the whole process Thus, TFA-MOD is regarded as one of the most suitable candidates for fabricating a YBCO tape for many high-power applications This method originated from an electron beam process using BaF2 developed by Mankiewich et al Afterwards, Gupta et al reported using TFA-MOD to prepare a similar precursor film These two ex situ processes used fluorides instead of BaCO3 to avoid the fatal deterioration in Jc, which is caused in the resulting films through metal carboxylic groups Fluorides not only avoid such deterioration but also lead to perfectly c-axis-oriented epitaxial crystal growth In conventional metalorganic deposition, nucleation in the precursor film causes random orientation in the resulting film However, in TFA-MOD, nanocrystallites in the precursor film never cause such disorder Furthermore, during the firing process of TFA-MOD, water and HF gas diffuse quickly between the film surface and growth front of the YBCO layer This diffusion never limits the growth rate of YBCO What distinguishes TFA-MOD from conventional metalorganic deposition? What happens during heat treatment? In this paper, we discuss all the TFA-MOD processes and the peculiar growth scheme of the YBCO layer in TFA-MOD using the model of a quasi-liquid network In addition, we review the history of TFA-MOD and recent results and discuss the prospects of future applications

https://iopscience.iop.org/article/10.1088/0953-2048/16/11/R01/pdf

Review of a chemical approach to YBa2Cu3O7−x-coated superconductors—metalorganic deposition using trifluoroacetates

We report on a new process to make films of Y1Ba2Cu3O7 using coevaporation of Y, Cu, and BaF2 on SrTiO3 substrates. The films have high transition temperatures (up to 91 K for a full resistive transition), high critical current densities (106 A/cm2 at 81 K), and a reduced sensitivity to fabrication and environmental conditions. Because of the lower reactivity of the films, we have been able to pattern them in both the pre‐annealed and post‐annealed states using conventional positive photoresist technology.

Reproducible technique for fabrication of thin films of high transition temperature superconductors

A series of GaInAs/InP quantum wells from 10 to 135 A has been grown by atmospheric organometallic vapor phase epitaxy using pressure balancing techniques. These wells exhibit strong exciton peaks at 4 K and have quantized energy shifts of up to 326 meV. These energy shifts are compared with two simple finite well models (Kronig–Penney and envelope function approximation) using a conduction‐band offset of Vc≊40% ΔEg(GaInAs) and are in close agreement with the latter model. The full width half‐maximum linewidths indicate an average interface roughness of ≊1 monolayer.

High quality narrow GaInAs/InP quantum wells grown by atmospheric organometallic vapor phase epitaxy

Full widths at half‐maximum intensity of the (004) Bragg reflecton peak as small as 24 arcs are obtained from InGaAs epilayers 4–6 μm thick. Such linewidth is the narrowest reported thus far for an InGaAs epilayer grown by any vapor phase technique reported in literature. Such extreme compositon uniformity is also supported by results from Auger depth profiles and 2 K photoluminescence measurements. Very intense efficient luminescence peaks due to excitonic transitions with linewidths (FWHM) as narrow as 1.2 meV are obtained. This again represents the narrowest linewidth ever reported for InGaAs grown by any technique. In fact, such a linewidth represents the narrowest linewidth ever measured for any alloy semiconductor. Further, the photoluminescence spectra reveal the donor‐to‐acceptor pair recombination is nearly absent. This indicates that the InGaAs is of very high purity. Hall measurements of 2–5‐μm‐thick epilayers grown directly on InP substrates have mobilities of 10 000–12 000 and 40 000–57 000 c...

Chemical beam epitaxial growth of extremely high quality InGaAs on InP

By using glass substrates which approximate the thermal expansion of a deposited Si film, thermal stress cracking during laser crystallization is eliminated. Results on three types of transparent silicate glass are reported. Chemical vapor deposition is used to coat these substrates first with a buffer layer of SiO2 or Si3N4 and then with a Si film. When the Si films are melted with an argon ion laser beam, large crystal grains are produced. Secondary ion mass spectroscopy is used to determine the effectiveness of the buffer layer in isolating the Si from impurities in the glass.

Laser crystallization of Si films on glass

The authors have demonstrated proximity effect coupling between a high-transition-temperature superconductor and a normal metal. In a device with a 1- mu m long gap in a YBa/sub 2/Cu/sub 3/O/sub 7/ film spanned by an Au shunt, the authors observed a DC supercurrent and the AC Josephson effect under microwave irradiation from 2 GHz to 15 GHz. Preliminary work has also begun with Ag shunts. It is concluded that these high quality S-N (superconductor-normal) interfaces should be applicable both to probing the superconducting state in oxide superconductors and to building high-T/sub c/ electronic devices. >

A. H. Dayem

Papers

Reproducible technique for fabrication of thin films of high transition temperature superconductors

High quality narrow GaInAs/InP quantum wells grown by atmospheric organometallic vapor phase epitaxy

Chemical beam epitaxial growth of extremely high quality InGaAs on InP

Laser crystallization of Si films on glass

The observation of the AC Josephson effect in a YBa/sub 2/Cu/sub 3/O/sub 7//Au/YBa/sub 2/Cu/sub 3/O/sub 7/ junction