N.L. Tran , J.Z. Sexton, T.J. Grassman, B. Fruhberger, A.C. Kummel

1. Data Acquisition And Control PC Mass Flow Control Exhaust Temperature Controlled Enclosure Test Chamber Heat Exchanger Flow Meter 4-Way Valve Temperature Controlled Bubblers Carrier Gas 1 2 3 rotary feedtrough (transfer shutter) electrical feedtroughs Cabling (stainless steel) Instrument Features: - Additional He gas cooled radiation shield in between to improve the thermal isolation baffles - Eddy current vibration damping of the pendulum motion of the inner cryostat linear feedtrough 4” (to pull down the STM) LN2 dewar (14 l) - STM is completely isolated (thermally and electrically) when tunneling LHe dewar (4 l) He gas cooled radiation shield STM-contacts (37-pin plug) radiation shields (LN2, LHe) shutter for sample & tip transfer STM head (a) 8K STM image of TBPP (porphyrin) on Cu(100), (b) STM simulation of TBPP/Cu(100); (c) structure of TBPP on Cu(100). Note the excellent submolecular resolution at the good agreement with the simulation. From Moresco et al eddy current damping for the LHe cryostat Instrumentation and Facilities for UCSD MURI N.L. Tran, J.Z. Sexton, T.J. Grassman, B. Fruhberger, A.C. Kummel University of California, San Diego S.V. Patel, T.E. Mlsna Seacoast Science AFOSR MURI# F49620-02-1-0288 DFT Computation Goal Determination of Material Growth and Analyte Interaction DEbinding of Cl2 using GGA-DFT • Develop Instruments to: • Fabricate Metallo-Phthalocyanine (MPC) Chemically Sensitive Field Effect Transistor (ChemFet) • Test MPC ChemFETs • Image Sensor Materials Computation suggest multiple possible binding sites for Cl2 (Cu and the organic ligand) Current Capabilities: • Room temperature STM • Filled state image of CuPc on Au(111) at monolayer coverage • Metal center of adsorbed CuPc appears dark, consistent with unfilled Cu-dz2 orbitals • Conditions: -1 V sample bias, 0.3 nA tunneling current DFT simulations can aid in the assignment of observed STM features Phthalocyanine Deposition 60 Å x 60 Å • Custom designed MBE cell for MPc deposition Low T effusion cell In Preparation: Evaluation of Sensor Performance Low Temperature STM for Single Molecule Studies: funded by NSF Linear & Linear/Rotary feedthroughs control plate valve Two mounted tees to connect shafts to feedthroughs The Createc STM-SY-014-2 combines a low-temperature STM (LT-STM) with three chambers: load-lock, sample preparation, and analysis. Two side ports for mounting turbo pump and ion gauge • Scanner: Beetle type with x-,y-coarse movement • Cooling: Liquid He bath cryostat; Scanner 100% surrounded by a 4K shield • Vibration isolation: Internal spring system with eddy current damping and external isolation with pneumatic isolation leg • Additional shutter to control in-situ gas dosing at low temperature onto STM mounted sample • Temperature variation either by heating the complete STM scanner or just the sample Cu cooling shield braised onto SS can • MBE cell capabilities include: • fast introduction of different MPcs • differential pumping • H2O cooled Cu heat shield to minimize heat transfer and protect UHV instrumentation • plate valve allowing separation between MBE cell and UHV chamber • 50 electrical feedthroughs • Closed-loop temperature control: 0 - 100 ± 0.05° C; 20 minute response time • Closed-loop relative humidity control: 0 - 100% ± 2% RH; 10 minute response time • Open-loop permanent gas concentration control: 0 - 40000 ± 4 ppm; 4 minute response time; or, • Open-loop volatile organics concentration control: up to 8 volatile organics from temperature-controlled bubblers in any one experiment, 4 minute response time • Temperature and humidity sensors inside chamber • Outer enclosure with closed-loop temperature control: 25 ± 0.5°C • Test runs are fully automated Effusion cell shutter Plate valve High Resolution Images of Complex Molecules At Low Temperature due to Extremely Stable Environment • Plate valve mechanics: Cu spacers for heat transfer – also act as hard stops Linear feedthrough Viton o-ring for sealing Future Plans Open to UHV And for deposition Closed to UHV • Use STM to image growth modes and analyte binding sites for Metallo-Phthalocyanines • Test sensors for ppb sensitivity and selectivity to Chemical Warfare Agent (CWA) simulants Cu plate Linear/rotary feedthrough