Monolithic fabrication of nano-to-millimeter scale integrated transistors based on transparent and flexible silicon nanonets

Abstract

In this paper, silicon nanonets (SiNNs), a synonym of random networks of silicon nanowires (SiNWs), are demonstrated as a potential alternative to replace amorphous silicon (a-Si) or organic materials in flexible and large-area electronics. We first report the low temperature and monolithic integration of SiNW-based field-effect transistors (FETs) with a channel length varying from a micro-to-millimeter scale. For a channel as long as 1000 μm, the current has to flow through a succession of at least a hundred SiNWs and as many SiNW–SiNW junctions. Despite this substantial related number of resistances in series, devices exhibit outstanding performances: a high drain current up to 10−7 A, an IOn/IOff ratio as large as 105 and a better mobility compared to a-Si and organic materials. Furthermore, such 1000 μm long channel FETs exhibit better subthreshold slope and lower device-to-device variability compared to shorter channel ones (50–200 μm). Good electrical stability is also observed after 4 months of exposure in air. In addition to these excellent features as a very long channel of transistors, silicon nanonets show good optical transparency and mechanical flexibility. These reported works make SiNNs a promising material for flexible and large-area electronics.

Optimization of GOPS-Based Functionalization Process and Impact of Aptamer Grafting on the Si Nanonet FET Electrical Properties as First Steps towards Thrombin Electrical Detection

“…Considering the as-fabricated devices, one can notice that increasing the channel length improves the reproducibility from one device to another. Such a phenomenon arises from the nanonet properties as previously shown [ 13 ]. Indeed, increasing the channel length results in a better averaging effect of the network so that the overall dispersion of the transistor parameters decreases when the channel length increases.…”

“…The fabrication of Si NN–FETs has already been reported by our group [ 13 , 14 , 25 , 26 ]. The process begins with the formation of a randomly oriented network from a suspension of Si nanowires elaborated by chemical vapor deposition (CVD) using a vapor–liquid–solid (VLS) mechanism [ 12 ].…”

“…Another FET-type integration solution is the Si nanonets (Si NN), which are 2D networks of randomly oriented Si NWs, which can be transferred on a wide range of substrates and notably CMOS readout circuits. To our knowledge, apart from the results presented by our group about Si NN in view of DNA detection, ranging from Si NN fabrication [ 12 ], Si NN integration in FET devices to provide Si NN–FETs [ 13 ] and Si NN–FETs functionalization for DNA sensing [ 14 ], there have not been any other related works published yet.…”

“…Moreover, the electrical and chemical stability of the Si NWs are crucial, and passivation by an oxide layer more stable than native SiO 2 is required. Notably, we have shown that Si NN–FET devices passivated with an 8 nm thick Al 2 O 3 layer exhibited a high electrical stability throughout a study conducted over several months [ 13 ].…”

Role played by the nanowire/nanowire junctions in the electrical properties of semiconductor percolating silicon nanowire networks

“…Field effect transistors (FETs) based on a randomly oriented nanostructure networks, called nanonets 1,2 , have been proposed as an interesting alternative to single nanostructure-based devices. In addition to benefiting from the semiconducting properties of each nanostructure, this network configuration gives additional features such as facility of integration 3 , mechanical flexibility 4,5 , optical transparency 5,6 , fault tolerance and high reproducibility 1,7 . Moreover, network density and device geometry (length and width) of FETs allow to tune the electrical performances which offers another considerable degree of freedom compared to single nanostructure-based devices 8,9 .…”