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Shell Thickness-Dependent Tunable Threshold Voltage Single Quantum Dot Rectification Diode
journal contributionposted on 2018-01-16, 00:00 authored by Gopal Sankar Kenath, Rekha Mahadevu, Anand Sharma, Vinod K. Gangwar, Sandip Chaterjee, Anshu Pandey, Bhola N. Pal
Ambient atmosphere single colloidal quantum dot (QD) rectifying diode with tunable threshold voltage has been fabricated by using a type-II heterojunction core/shell structure with a device geometry ITO/ZnO/QDs. Specifically, in our work we have used ZnTe/CdS core/shell QDs in which hole wave function strongly confined to the core, whereas the lowest-lying conduction band state resides in the shell. Current–voltage (I–V) characterization of this device has been done using an ambient atmosphere scanning tunneling microscope. The scanning tunneling spectra (STS) shows high rectification with a ratio of 103. The rectification is found to arise because of the bias-dependent band alignment of ZnO/QDs heterojunction and the effect of shell of each QD that presents a barrier for hole tunneling into the substrate. This barrier is overcome by the externally applied bias. This mechanism is distinct from the rectification observed in conventional p–n junction diodes. In particular, we find that even for QDs with optical band gaps of ∼1 eV, the threshold voltage may be tuned from 1 to 3 V by regulating shell thickness.
diodehole tunnelingrectificationITOhole wave functiontunable threshold voltageheterojunction10 3corebarrierbias-dependent band alignmentscanning tunneling spectralowest-lying conduction band statethreshold voltagequantum dot3 Vambient atmosphere scanning tunneling microscopeshell Thickness-Dependent Tunable Threshold Voltage Single Quantum Dot Rectification Diode Ambient atmosphereSTSdeviceband gapsshell thicknessQD