Green synthesis of germanium nano ink and inkjet printing of Si/Ge heterostructure

We present a green route of synthesis of germanium nanocrystals by cryomilling. The particles (similar to 80 nm) are further functionalized with acrylic acid and dispersed in the isopropyl alcohol (IPA) medium to obtain colloidal ink suitable for inkjet printing under ambient atmosphere to form device grade structure. Printing on silicon wafers presents a complex problem of coffee-ring pattern formation that hinders the printing quality. Enhancing the printing quality can be realized by controlling the hydrophobicity of the silicon surface by optimizing termination of the surface bond through a cleaning protocol and temperature of printing. Through a simple model architecture using n-type Si (001) substrate, the diode performance of the Si/Ge printed heterostructure that has the potential to evolve into a cost-effective development of semiconducting devices is demonstrated.