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Non-hysteretic positioner for nano-lithography and cryogenic in situ adjustable nano-junctions : 

Non-hysteretic positioner for nano-lithography and cryogenic in situ adjustable nano-junctions Benjamin Thomsen and Jesper Mygind* Department of Physics, B309, Technical University of Denmark, Lyngby Denmark. *E-mail: Work supported in part by INTAS projects 01-0809 and 01-0686, Danish Natural Science Foundation, and the Hartmann Foundation.


Overview Motivation direct writing of nano devices (Al or Ti films on Si @ 300K) cryogenic in situ adjustable nano-junctions millikelvin operation (KelvinOx 3He/4He fridge) The integrated nano-positioner prototype scanner head (AFM, STM, SNOM), optical guides, focusing lens sample positioner (X-Y translator, Z-translator) working principle, friction motor, step-length, non-hysteretic ) Veeco/Digital controller and the PC/LabView motor driver Results, Z-translator, X-Y translator Conclusion and outlook writing of nano devices optical interferometric coarse X-Y-Z position, closed loop operation 32 mm dia miniature nano-positioner


Schematic of integrated cryogenic positioner AFM , STM or SNOM head with X-Y-Z tube scanner Sample table with thermometers and bias connections X-Y-translator body Z-motor body Z-motor with sapphire prism, 4 steel balls and 4 shear stacks Sample X-Y-motor with 3 steel balls and 6 “legs” Spring leaf adjustment for X-Y motor Input /output optical fibers


The Z-positioner 2 shear actuators 4 steel balls Sapphire prism Old principle: friction motor with 6 shear actuators New positioner: steel balls/graphite gliders, variable step length


Working principle of friction motor Problems with uneven friction (only 4 actuators are shown)


Friction-motor, working principle one leg moves forward while all other legs stand All legs and the rod move backwards One can stop here !


The four curves correspond to two translations in both directions. The voltage ramp used to step the cylinder starts at ± 200 V, decreasing to ± 75 V, where the movement has stopped, and then increasing again to ± 200 V. Z-motor with sapphire rod positive negative


Novel working principle for both Z- and X-Y-translator


One leg for the novel translator with both X- and Y-motion polished glued to brass base electrodes shown in blue and red


X-Y translator with two sets of 3 legs The 2 x 3 legs are placed equidistantly on a circle. Each leg has an X-Y shear stack and a multilayer Z-stack Working principle: The quartz plane, which is pressed against the 3 (red) steel balls, is translated in the X-Y plane by the alternating action of the two sets (green and blue) of 3 legs


X-Y-motor assembled Mirror for optical interferometer Quartz plate 6 piezo legs Top plate Body Leaf spring


X-Y-motor dismantled Quartz disk 3 steel balls 6 piezo legs body Top part with quartz disk Leaf spring


- 200V +200V 0V  200 V  X = Y = 1300 nm Fringe pattern from optical interferometer


Writing of nano structures in 2nm thick Ti-film

Conclusion and outlook: 

Conclusion and outlook Cryogenic AFM head is being tested Optical interferometric coarse X-Y-Z position with closed loop operation 32mm dia miniature nano-positioner Has been achieved The cryogenic Z-motor with STM head operates with atomic resolution The X-Y-motor prototype works well at 300K Writing of nano devices at 300K works Future work

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