R. Singh

Some photoeffect roles in rapid isothermal processing

When compared to furnace processing, for identical and lower substrate temperatures, more photons are available in the visible and ultraviolet regions for rapid isothermal processing (RIP) based on incoherent radiation as the energy source. In this letter, we provide experimental evidence for photoeffects in RIP for a wide variety of materials. As compared to furnace processed samples, rapid isothermal annealed phosphosilicate glass films on Si substrate show a higher value of refractive index, a lower flatband charge density, and a lower thermal stress. High‐temperature superconducting thin films on Y‐Ba‐Cu‐O deposited by RIP assisted metalorganic chemical vapor deposition on yttrium stabilized zirconia substrate show a larger grain size, a higher value of the transition temperature than their furnace counterpart. The microscopic understanding of a particular deposition or annealing process is necessary to take full advantage of photoeffects in RIP.

Superconducting thin films of Y-Ba-Cu-O prepared by metalorganic chemical vapor deposition

High throughput, low‐temperature deposition, sharp interfaces, and selective deposition with direct ion‐, electron‐, and photon‐beam‐controlled techniques are some of the key driving forces for the development of superconducting thin films by metalorganic chemical vapor deposition (MOCVD) technique. In this paper we report on the electrical and structural properties of Y‐Ba‐Cu‐O (YBCO) films deposited by MOCVD on yttrium‐stabilized zirconia (YSZ) and BaF2/YSZ substrates using a single‐step in situ processing method which requires no further annealing. YBCO films deposited on BaF2/YSZ substrates have zero resistance at 80 K. The films were characterized by energy dispersive x‐ray analysis, x‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The films on BaF2/YSZ substrates exhibited textured growth having both the c and a axis perpendicular to the substrate. The use of BaF2 as a buffer layer suggests three‐dimensional integration of high‐temperature superconducting thin f...

Preparation of BaF2 films by metalorganic chemical vapor deposition

To date thin films of II(a) fluorides (CaF2, BaF2, SrF2, and their mixtures) have only been deposited by physical vapor deposition techniques. We report for the first time the deposition of BaF2 films on silicon and yttrium‐stabilized zirconia substrates by metalorganic chemical vapor deposition at a substrate temperature as low as 400u2009°C.

Comparative study of phosphosilicate glass on (100) silicon by furnace and rapid isothermal annealing

Annealing experiments were carried out on phosphosilicate glass (PSG) films deposited on (100) silicon substrates by using a low‐pressure chemical vapor deposition technique. Rapid isothermal processing and conventional furnace heating were used to study the electrical, structural, and mechanical characteristics of these films and the results of the two processes compared. A refractive index of 1.457 was obtained in the rapid isothermal annealing cycle of 800u2009°C/15S, but was 1.419 for the furnace annealing cycle (i.e., 800u2009°C/65S). Spreading resistance analysis has shown that the junction depth remains unchanged for an 800u2009°C/15S rapid isothermal annealing cycle. Stress measurements show that rapid isothermal annealing leads to less strain compared to furnance annealing. The x‐ray photoelectron spectroscopy analysis shows that as compared to furnance annealing, rapid isothermal annealing provides a chemically homogenous interface. High‐frequency capacitance voltage (C‐V) measurements show that furnance‐an...

Preparation of BaF sub 2 films by metalorganic chemical vapor deposition

To date thin films of II(a) fluorides (CaF2, BaF2, SrF2, and their mixtures) have only been deposited by physical vapor deposition techniques. We report for the first time the deposition of BaF2 films on silicon and yttrium‐stabilized zirconia substrates by metalorganic chemical vapor deposition at a substrate temperature as low as 400u2009°C.

Reduced thermal budget processing of Y-Ba-Cu-O films by rapid isothermal processing assisted metalorganic chemical vapor deposition

Metalorganic chemical vapor deposition (MOCVD) has the potential of emerging as a viable technique to fabricate ribbons, tapes, coated wires, and the deposition of films of high‐temperature superconductors, and related materials. As a reduced thermal budget processing technique, rapid isothermal processing (RIP) based on incoherent radiation as the source of energy can be usefully coupled to conventional MOCVD. In this paper we report on the deposition and characterization of high quality superconducting thin films of Y‐Ba‐Cu‐O (YBCO) on yttrium stabilized zirconia substrates by RIP assisted MOCVD. Using O2 gas as the source of oxygen, YBCO films deposited initially at 600u2009°C for 1 min and at 745u2009°C for 25 min followed by deposition at 780u2009°C for 45 s are primarily c‐axis oriented and zero resistance is observed at 89–90 K. The zero magnetic field current density at 53 and 77 K are 1.2×106 and 3×105 A/cm2, respectively. By using a mixture of N2O and O2 as the oxygen source substrate temperature was furthe...

Role of in situ rapid isothermal processing in the solid phase epitaxial growth of II‐A fluoride films on (100) and (111) InP

Rapid isothermal processing based on incoherent sources of light is emerging as a reduced thermal budget processing technique for the fabrication of next generation of semiconductor devices and circuits. In this letter, we show that integration of the rapid isothermal processing unit and the ultrahigh vacuum deposition system provides an in situ rapid isothermal processing capability for the solid phase epitaxial growth of SrF2 and BaF2 films on (100) and (111)InP. We also show that neither as‐deposited nor ex situ annealed films show solid phase epitaxial growth.

In situ deposition of BaF2 as a buffer layer and the superconducting thin films of Y‐Ba‐Cu‐O on silicon substrates by metalorganic chemical vapor deposition

High throughput, sharp interfaces, and selective deposition with direct ion‐, electron‐, and photon‐beam‐controlled techniques are some of the key driving forces for the development of superconducting thin films by the metalorganic chemical vapor deposition technique. In this paper, we report on the in situ deposition of a buffer layer of BaF2 and high‐temperature superconducting thin films of Y‐Ba‐Cu‐O by metalorganic chemical vapor deposition (MOCVD) on silicon substrates. These films have an on‐set temperature of 90 K and zero resistance at 73 K. The use of BaF2 as a buffer layer on Si substrates suggests the possibility of three‐dimensional integration with high‐temperature superconducting thin films, for hybrid superconductor/semiconductor devices as well as superconducting switches and other related devices. To the best of our knowledge, this is the first report of the deposition of high‐temperature superconducting thin films on Si by MOCVD.

Relationship between thermal stress and structural properties of SrF2 films on (100) InP

The measurement of thermal stress of SrF2 films on InP as a function of temperature is presented. The in situ and ex situ rapid isothermal annealed films have different values of thermal stress at room temperature and show entirely different behavior of thermal stress during heating and cooling cycles. X‐ray photoelectron spectroscopy measurements were used to characterize the surface of the SrF2 films as well as the SrF2/InP interface for both the ex situ and in situ annealed films. It is shown that the difference in the microstructure of in situ and ex situ rapid isothermal annealed SrF2 films on InP is indeed reflected in the significant difference in the thermal stress.

Solid phase epitaxial growth of II-A fluorides on semiconductors by In-Situ rapid isothermal processing

In general, during the deposition of epitaxial dielectrics, the substrate is heated at elevated temperatures, which is undesirable for a number of applications. In this paper we report the use of in-situ rapid isothermal processing for the solid phase epitaxial growth of CaF2 on Si (111) and BaF2 and SrF2 on InP (100) substrates. X-ray diffraction, TEM, SEM, and XPS studies of grown films have clearly established the superiority of in-situ annealing over ex-situ annealing.