We present investigation s of surface state electrons on liquid helium film in confine geometry, using a suitable substrate structure microfabricated on a silicon wafer, s imilar to a Field Effect Transistor (FET). The sample 'has a SOUl'ce and drain region , separated by a gate structure, wh ich consists of two go ld electrodes with a narrow gap (channel) through which the tran sport ofthe surface state electrons takes place. The sampie is illuminated to provide a sufficien number of free carriers in the sili con substrate, such that a well-define potential distribution is ac hieved. The eventual goa l ofthese experiments is to study the electron transport through a narrow channel in the variolls states ofthe ph ase diagram ofthe 2D e lectron system. In th e present work we focus on storing the electrons in the source area of the FET, and investigate the spatial distribution of these electrons. lt is shown that under the influ ence of a potential g radi ent in the sili con substrate the e lectron s accllmulate in front of the potential barri er of the gate. The electron di stribution, governed by Coulomb repulsion and by the substrate potentia l, is determin ed ex perim entally. The result is found to be in good agreement w ith a parallel-plate capacitor mode l of the system, developed with the aid of a finit element ca lculation of the surface potential profil of th e device.
We present transport measurements of surface-state electrons on liquid helium films in confined geometry. The measurements are taken using split-gate devices similar to a field effect transistor. The number of electrons passing between the source and drain areas of the device can be precisely controlled by changing the length of the voltage pulse applied to the gate electrode. We find evidence that the effective driving potential depends on electron-electron interactions, as well as the electric field applied to the substrate. Our measurements indicate that the mobility of electrons on helium films can be high and that microfabricated transistor devices allow electron manipulation on length scales close to the interelectron separation. Our experiment is an important step toward investigations of surface-state electron properties at much higher densities, for which the quantum melting of the system to a degenerate Fermi gas should be observed.
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