Frank Dimeo

A new route to high‐Tc superconducting Bi–Sr–Ca–Cu–O thin films: Improved deposition efficiency and film morphology using ammonia–argon mixtures as the carrier gas

Highly oriented films of the high‐Tc superconductor Bi2Sr2CaCu2Ox have been prepared by a low‐pressure organometallic chemical vapor deposition process using a mixture of ammonia and argon as the carrier gas together with Sr(dpm)2 (dpm‐dipivaloylmethanate), Ca(dpm)2, Cu(acac)2 (acac‐acetylacetonate), and triphenylbismuth as the organometallic precursors. By introducing ammonia into the carrier gas, a significant improvement in the volatility and thermal stability of both Sr(dpm)2 and Ca(dpm)2 is observed. Typical required source temperatures for Sr(dpm)2 and Ca(dpm)2 with the introduction of ammonia are about 40–50 °C lower than the source temperatures of the precursors without the introduction of ammonia. Enhancement of source volatility for Cu(acac)2 is also observed. After annealing at 865 °C in flowing oxygen, the films consist predominantly of the Bi2Sr2CaCu2Ox phase and exhibit high preferential orientation of the crystallite c axes perpendicular to the substrate surface. Four‐probe resistivity meas...

ATMI’s Ion Implant Process Efficiency Research Laboratory (IIPERL)

We describe an ion source test stand recently installed by ATMI, and show data illustrative of the research being carried out at the new facility.

The Development of In‐Situ Ion Implant Cleaning Processes

Considerable gains in implanter utilization efficiency can be attained with in‐situ cleaning of deposited material, particularly in and around the ion source. Different methods of in‐situ cleaning are described, and we discuss the relative merits of several chemical reagents. We introduce XeF2, a new and promising reagent for in‐situ cleaning and present some preliminary experiments showing its ability to etch dopant materials. We also show that in some cases etching by XeF2 can be selective with respect to ion source construction materials such as tungsten.

Solid phase epitaxy of Bi2Sr2CaCu2Ox superconducting thin films

Epitaxial superconducting Bi2Sr2CaCu2Ox (BSCCO) thin films have been formed by solid phase epitaxy from amorphous films deposited by metallorganic chemical vapor deposition. (100) MgO and LaAlO3 single crystals were used as the substrates. After high‐temperature annealing in flowing oxygen, the films consist predominantly of the BSCCO (2212) phase and are epitaxial to the LaAlO3 with the c axis perpendicular to the substrate surface. The epitaxial structure of the films is confirmed by x‐ray diffraction measurements including θ/2θ and in‐plane Φ scans as well as by cross‐sectional high‐resolution transmission electron microscopy. Four‐probe resistivity measurements show that the critical temperature of the film on LaAlO3 is 78 K. The critical current density of the epitaxial layer was one order of magnitude greater than that of textured films on MgO.

The Influence of Weak Links and Oxygen Deficiency on Electrical Properties of Bi-2212 and Ti-2212 Hts Thin Films

Thin films of the Bi-2212 and T1–2212 compounds were prepared by MOCVD deposition techniques. Resistivity versus temperature and critical current density measurements were used to characterize the electrical properties. An analysis of the data based on a proposed model determined the influence of intragranular weak links. Thin film samples in both systems with near optimum oxygen doping showed a correlation between the slope and magnitude of the resistivity in the normal state. Samples with reduced oxygen content displayed a strong increase in the intragrain boundary resistance, consistent with weak link defects. The results agree with a similar analysis of YBCO samples and support a common mechanism for the development of weak links in cuprates.

Microstructure and superconducting properties of BiSrCaCuO thin films

High-Ta superconducting Bi-Sr-Ca--Cu-0 thin films have been prepared by low pressure organometallic chemical vapor deposition (ONCVD). Factors which influence texture and morphology of the OMCVD derived films have been examined, including the effects of precursors, doping and substrates. Under optimal conditions, high quality films with a high degree of preferred orientation are obtained. Initial experiments on in-situ formation of superconducting films are also described.

In Situ Heteroepitaxial Bi 2 Sr 2 CaCu 2 O 8 Thin Films Prepared by Metalorganic Chemical Vapor Deposition

Bi 2 Sr 2 CaCu 2 O 8 thin films have been prepared in situ by low pressure metalorganic chemical vapor deposition using fluorinated β–diketonate precursors. The influence of the growth conditions on the oxide phase stability and impurity phase formation was examined as well as the superconducting properties of the films. Thin films deposited on LaAIO 3 substrates were epitaxial as confirmed by x-ray diffraction measurements, including θ-2θ and φ scans. Four probe resistivity measurements showed the films to be superconducting with a maximum T c0 of 90 K without post annealing. This T c0 is among the highest reported for thin films of the BSCCO (2212) phase, and approaches reported bulk values.

Solid phase epitaxy of Bi2Sr2CaCu2O x superconducting thin films

Epitaxial superconducting Bi2Sr2CaCu2Ox (BSCCO) thin films have been formed by solid phase epitaxy from amorphous films deposited by metallorganic chemical vapor deposition. (100) MgO and LaAlO3 single crystals were used as the substrates. After high‐temperature annealing in flowing oxygen, the films consist predominantly of the BSCCO (2212) phase and are epitaxial to the LaAlO3 with the c axis perpendicular to the substrate surface. The epitaxial structure of the films is confirmed by x‐ray diffraction measurements including θ/2θ and in‐plane Φ scans as well as by cross‐sectional high‐resolution transmission electron microscopy. Four‐probe resistivity measurements show that the critical temperature of the film on LaAlO3 is 78 K. The critical current density of the epitaxial layer was one order of magnitude greater than that of textured films on MgO.

Solid phase epitaxy of Bi2Sr2CaCu2Oxsuperconducting thin films

Epitaxial superconducting Bi2Sr2CaCu2Ox (BSCCO) thin films have been formed by solid phase epitaxy from amorphous films deposited by metallorganic chemical vapor deposition. (100) MgO and LaAlO3 single crystals were used as the substrates. After high‐temperature annealing in flowing oxygen, the films consist predominantly of the BSCCO (2212) phase and are epitaxial to the LaAlO3 with the c axis perpendicular to the substrate surface. The epitaxial structure of the films is confirmed by x‐ray diffraction measurements including θ/2θ and in‐plane Φ scans as well as by cross‐sectional high‐resolution transmission electron microscopy. Four‐probe resistivity measurements show that the critical temperature of the film on LaAlO3 is 78 K. The critical current density of the epitaxial layer was one order of magnitude greater than that of textured films on MgO.