Nanoelectronic devices and measurements toward nanocrystal-based optoelectronics and DNA sequencing with solid-state nanopores

Nanoelectronics are critical to exploring nanoscale materials: including nanocrystals, which could revolutionize optoelectronics, and DNA, which could revolutionize medicine. Our suspended silicon nitride membranes combined with electron beam lithography and transmission electron microscopy have been essential to our device fabrication and measurements. Nanocyrstal-based optoelectronics have garnered much interest, and thus new ways of increasing their transport are constantly being researched. We used ligand exchanges to decrease the interparticle spacing of nanocrystal films, which is known to augment transport. Using gaps only a few nanoparticles-wide, we measured transport and found that current could be controlled with annealing, hydrazine treatment, and voltage-sweeping. Annealing destroyed the insulating ligand surrounding each nanocrystal and allowed the particles to move closer. This usually increased the photocurrent, without significantly increasing the dark current. However, this was ineffective on sub-monolayers. Hydrazine was similar, except it replaced the ligand, rather than destroying it, and it was effective on sub-monolayers; however, it caused a large increase in the dark current as well as the photocurrent. Sweeping the voltage overnight could increase or decrease the photocurrent of a sample depending on whether the sample was illuminated or in the dark, corresponding to traps being emptied or filled. In addition to nanocrystals, our devices were used in solution to sense DNA. We fabricated nanelectrodes and nanowires next to nanopores and showed DNA translocations ionically. We also developed methods to make the pores hydrophilic without the use of piranha; we instead used rapid thermal annealing, heated ozone treatments, and oxygen/hydrogen plasmas. While high rates of device failure was a challenge, recommendations for future experiments are presented, including grounding of all equipment and an extreme focus on sample cleanliness. We have shown that our nanoelectronics can be successfully integrated into nanocrystal optoelectronics and DNA nanopore sequencing devices. We hope that the exploration of both our successes and failures will advance nanoelectronics and their applications.