Date of Graduation
Master of Science in Materials Science
Physics, Astronomy, and Materials Science
thin films, heterostructure, 2D materials, hafnium disulfide, hafnium dioxide, atomic layer deposition, hydrothermal synthesis
Condensed Matter Physics
Heterostructures have been utilized in electronic devices for over 50 years with the proposal for the first heterostructure transistor in 1957. With the scaling of devices, it is necessary to create new heterostructures that will comply with Moore’s Law, as well as make devices faster and consume less power. Novel 2D materials, such as hafnium disulfide, have shown promise as an active channel layer, while hafnium dioxide is already proven to be a replacement of silicon dioxide for the gate insulating layer. However, fabrication techniques for wide-scale integration of these heterostructures have not yet been achieved. Also, the dielectric properties of hafnium dioxide must be realized before it can be used as a replacement of silicon dioxide. Dielectric spectroscopy results indicate that the dielectric constant for the samples was between 15-29, with sample 2 showing the highest dielectric constant of 28.8 and the lowest range of dielectric loss when measured from 200 Hz to 90 kHz. However, the results also indicate that proper contact of the probe with the electrodes is necessary to minimize error. Thus, the erroneous values at some frequencies could be attributed to poor ohmic contact of the probes, or a miscalibration of the system. I have also shown that hafnium disulfide layers can be created by converting some top layers of HfO2 thin films through sulfidation in hydrothermal process, thus demonstrating that creating a HfO2/HfS2 heterostructure is possible. XRD analysis shows a broad peak after sulfidation that relates to hafnium oxysulfide. In addition, the Raman analysis indicates that hafnium disulfide is present after sulfidation of hafnium dioxide.
© Christopher J. Robledo
Robledo, Christopher J., "Heterostructure of 2D Materials: HfS2/HfO2/Si" (2020). MSU Graduate Theses. 3550.