Low-Frequency (1/<i>f</i>) Noise in Nanocrystal Field-Effect Transistors

We investigate the origins and magnitude of low-frequency noise in high-mobility nanocrystal field-effect transistors and show the noise is of 1/<i>f</i>-type. Sub-band gap states, in particular, those introduced by nanocrystal surfaces, have a significant influence on the 1/<i>f</i> noise. By engineering the device geometry and passivating nanocrystal surfaces, we show that in the linear and saturation regimes the 1/<i>f</i> noise obeys Hooge’s model of mobility fluctuations, consistent with transport of a high density of accumulated carriers in extended electronic states of the NC thin films. In the subthreshold regime, the Fermi energy moves deeper into the mobility gap and sub-band gap trap states give rise to a transition to noise dominated by carrier number fluctuations as described in McWhorter’s model. CdSe nanocrystal field-effect transistors have a Hooge parameter of 3 × 10^–2, comparable to other solution-deposited, thin-film devices, promising high-performance, low-cost, low-noise integrated circuitry

<i>In Situ</i> Repair of High-Performance, Flexible Nanocrystal Electronics for Large-Area Fabrication and Operation in Air

Colloidal semiconductor nanocrystal (NC) thin films have been integrated in light-emitting diodes, solar cells, field-effect transistors (FETs), and flexible, electronic circuits. However, NC devices are typically fabricated and operated in an inert environment since the reactive surface and high surface-to-volume ratio of NC materials render them sensitive to oxygen, water, and many solvents. This sensitivity has limited device scaling and large-scale device integration achievable by conventional fabrication technologies, which generally require ambient air and wet-chemical processing. Here, we present a simple, effective route to reverse the detrimental effects of chemical and environmental exposure, by incorporating, <i>in situ</i>, a chemical agent, namely, indium metal, which is thermally triggered to diffuse and repair the damage. Taking advantage of the recovery process, CdSe NC FETs are processed in air, patterned using the solvents of lithography, and packaged by atomic layer deposition to form large-area and flexible high-performance NC devices that operate stably in air