Using a time-of-flight technique, different transport mechanisms, deep trapping, multiple shallow trapping, and ideal itrinsic transport, can be observed in the different temperature and phase regions of the liquid-crystalline photoconductor hexapentyloxytriphenylene. The temperature and field dependences of carrier mobilities up to 1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ ${\mathrm{cm}}^{2}$/V s have been determined; this value exceeds considerably the mobilities of the most commonly used organic photoconductors. The experiments reflect a variety of transport phenomena which are novel in the field of liquid-crystalline systems.

Transient photoconductivity in a discotic liquid crystal.

Diffusion in thermotropic liquid crystals

Charge carrier transport in liquid crystals

The nematic liquid crystal is considered as a weak electrolyte. The analysis of the time behaviour of the transient current flowing through the sample allows the estimation of the mean mobility of anions and cations. The electrohydrodynamic flows are avoided thanks to the application of low voltages. For p-octyloxyphenyl p'-pentyloxybenzoate the measured values of mobility are = 0,9 · 10−6 cm2 V−1 s−1 and = 1,3 · 10−6 cm2 V−1 s−1 at 326K. The temperature behaviour of mobility and conductivity is described by identical activation energies: 0.48 eV and 0.16 eV in nematic and isotropic phase respectively.

Charge Carrier Mobility Measurements in Nematic Liquid Crystals

Stiction is one of the major reliability issues limiting practical application of nano-electro-mechanical systems (NEMS), an emerging device technology that exploits mechanical movements on the scale of an integrated electronic circuit. We report on a discovery that stiction can be eliminated by infiltrating NEMS with nematic liquid crystals. We demonstrate this experimentally using a NEMS-based tunable photonic metamaterial, where reliable switching of optical response was achieved for the entire range of nanoscopic structural displacements admitted by the metamaterial design. Being a more straightforward and easy-to-implement alternative to the existing antistiction solutions, our approach also introduces an active mechanism of stiction control, which enables toggling between stiction-free and the usual (stiction-limited) regimes of NEMS operation. It is expected to greatly expand the functionality of electro-mechanical devices and enable the development of adaptive and smart nanosystems.

https://pubs.acs.org/doi/pdf/10.1021/acsnano.6b07495

Controlling Stiction in Nano-Electro-Mechanical Systems Using Liquid Crystals

The electrical conductivity and the mobility measurements in nematic mixtures Merck 5 and Merck 7a are reported. The drift mobility of carriers about 10−5 cm2/Vs at room temperature was determined. Identical activation energies of conductivity and mobility were obtained (0.4 eV for Merck 7a and 0.3 eV for Merck 5). In our opinion, the conductivity of examined mixtures is controlled by ionic transport.

A. Lipinski

Papers

Charge Carrier Mobility Measurements in Nematic Liquid Crystals

The Study of the Charge Carrier Transport in Nematic Mixtures