Oxide molecular beam epitaxy (MBE)
The laboratory space dedicated for the proposed work is about 1300 square feet with two fume hoods and one laminar flow hood. The laboratory is located in the Amundson Hall 22 and accommodates all infrastructures needed to support a high vacuum system, such as liquid nitrogen, compressed air, nitrogen gas from liquid boil-off, and appropriate electrical outlets, chiller, etc.
The MBE system in the Prof. Jalan’s lab is fully operational and has already demonstrated the capability to grow highly perfect SrTiO3, NdTiO3 and BaSnO3 films (see Fig.5). This is a commercial system with a few customizations that PI has purchased from Omicron nanotechnology, Germany. Below is a short description of the MBE system. It consists of a UHV (< 10‐10 Torr) growth chamber, a UHV buffer chamber and a high vacuum load lock chamber. The main chamber has a cyro-pump (CP-8) and a magnetically levitated turbomolecular pump with a pumping speed of 2100 l/s allowing for ultra low-pressure ideal atmosphere for high purity growth. The main growth chamber has nine effusion cell ports, which are equipped with two high temperature effusion cells (< 2200 °C), two medium temperature effusion cells (<1100 °C), two low temperature gas sources and an auto-tuned rf plasma source for oxygen. The main chamber has an oxygen compatible SiC heater stage (up to 1200 °C in POx = 1× 10-5 Torr), a reflection high-energy electron diffraction set-up (RHEED), a residual gas analyzer (RGA), a quartz crystal monitor (QCM) mounted on a retractable rod in a load lock assembly allowing for easy replacement of crystals. The buffer chamber is set up for sample cleaning and annealing up to 1300 °C and can store five samples at a time for growth. Two gas sources are connected to a bubbler containing titanium and tin precursor respectively through two separate gas inlet system controlled by growth software integrated with the computer controlling the MBE system. Computer control over the entire system, including source shutters, mass flow control, heater stage temperature, and source power supplies, oxygen plasma power allows for completely automated growth of compounds, alloys, heterostructures, and superlattices.
UHV molecular beam epitaxy system
This is a home-built UHV metal MBE system with a base pressure below 10-10 Torr. The system incorporates a large ion pump, titanium sublimation pumps, sorption pumps (for roughing), a set of cryopanels, a residual gas analyzer, and a UHV (10-9 Torr) load lock chamber with in situ plasma etching capability. Deposition sources include a four-source linear electron beam evaporator and three thermal cells, which can be energized simultaneously for alloy growth. Growth can be monitored via two quartz crystal monitors and a sophisticated deposition controller capable of controlling rates down to 0.025 Å/s, as well as alloy growth from two sources. The system also includes a rotating x-y-z growth stage capable of temperatures up to 1200oC. In-situ structural characterization is achieved by RHEED (Reflection High Energy Electron Diffraction) with a 15 KV electron gun, beam rocking capability, and k-Space image acquisition and analysis software.
UHV sputter deposition system
This is a commercial system based on a modified version of the Kurt J. Lesker CMS 18 present in Prof. Leighton’s lab. The deposition system consists of a UHV (< 10-9 Torr) main chamber and a HV load lock chamber. The main chamber has a dry pumping system, the primary pump being a magnetically-levitated turbomolecular pump. The main process chamber has six confocal deposition sources (DC or RF), an oxygen compatible heater stage (up to 850 C), two mass flow channels (Ar and O2) and a residual gas analyzer. The load lock chamber is set up for annealing or cooling in an oxygen pressure up to 500 Torr. Sputtering is possible in total gas pressures up to about 150 mTorr, with 30 mTorr of O2. The deposition sources are powered by three (switchable) power supplies (two DC and one RF). Computer control over the entire system, including source shutters, mass flow control, heater stage temperature, and source power supplies, allows for completely automated growth of compounds, alloys, multilayers, and superlattices. An UHV sputter deposition system, a high-pressure oxygen sputter deposition system and a UHV molecular beam epitaxy system. We have just started using UHV sputter system to initiate thin film growth of NdTiO3. The deposition system consists of a UHV (< 10-9 Torr) main chamber and a HV load lock chamber, which allows for faster and easier sample exchange.
High pressure oxygen sputter deposition system
To the best of our knowledge this is the only system of its kind at a US university. Based on the Julich design, it is a three source sputter system designed to operate in pure oxygen at pressures up to several Torr. The unique design almost eliminates oxygen induced re-sputtering problems by thermalizing O ions via collisions with other ions in the dense plasma. The system is capable of deposition temperatures up to 1000 oC and the films can be cooled, post-deposition, in one atmosphere of O2. The system has demonstrated capability for deposition of high quality epitaxial films of cuprates, manganites, cobaltites, ferrites, titanates, etc.
Sulfide reactive deposition system
A home-built 3 source HV sputtering system for the reactive deposition of transition metal disulfides. The system has three 2” magnetron sources, a HV load lock chamber, a residual gas analyzer, a 700 oC substrate heater, and a gas flow system capable of handling a H2S/Ar mix as a reactive gas. The latter involves an exhausted gas cabinet, double-walled delivery lines, a corrosive series turbomolecular pump, a N2 dilution system, a rough pump in a fume hood, and a H2S detection system. This chamber has been used for the growth of thin films of CoS2 and FeS2.