Functionalizing van der Waals materials by shaping them

(Nanowerk News) PN junction is the elementary building block of semiconductor devices, like diode, solar cell and LED, which make up the modern (opto-)electronics.
Recently, researchers from the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences have proposed a novel method to fabricate two-dimensional PN junction. This method simplifies the semiconductor manufacturing process and is well-suited to develop (opto-)electronic devices at the ultimate physical limit.
The study was published in Light: Science & Applications ("Pristine PN junction toward atomic layer devices").
The researchers found that a number of Van der Waals materials do not need artificial doping, and they can dope themselves from n- to p- type conductance with an increasing/decreasing thickness. For example, MoTe2 material exhibits p-type, unintentional doping and n-type doping behaviors when it has one molecular layer, three molecular layers, and five molecular layer thickness, respectively.
"Using this novel property, we can easily fabricate atomically abrupt PN junctions on a variety of two-dimensional materials, which is out of the range of traditional techniques," said XIA Hui, first author of the study.
Moreover, there are no complicated photolithography and chemical doping processes in layered junction devices. Instead, it is only the geometry of the material that is needed to be shaped.
"These findings may open a new avenue to develop novel nanodevice applications, where the geometrical size becomes the only critical factor in tuning charge-carrier distribution and functionality," said XIA.
Source: Chinese Academy of Sciences
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