Synopsis:
Gadolinium oxide (Gd2O3) is of research interest as a replacement material for silicon dioxide in silicon-based electronics because of its high dielectric constant (κ = 14). Recently, we have discovered that films comprised of nanocrystalline Gd2O3 revealed intriguing charge storage characteristics, particularly when arranged as the oxide layer of a metal–oxide–semiconductor structure. We have fabricated such nanocrystalline films via electrophoretic deposition and have shown that our findings could lead to viable alternatives to silicon-based systems for a variety of electronics applications, such as non-volatile memory.
Major Achievements:
All nanocrystal films can be employed as charge storage, dielectric materials. A portion of this research is the subject of a patent application.
Detailed Discussion:
Gd2O3 in its bulk crystalline and amorphous phases has been of research interest as a replacement material for silicon dioxide in transistors and other electronic devices because of its relatively high dielectric constant ( vs. ). Discovery of a high-κ dielectric material, nanocrystalline or otherwise, could make possible a number of technological advances regarding computing (energy efficiency, processing speed) telecommunications (bandwidth, speed), among others. Recently, dielectric studies of amorphous Gd2O3 films, embedded with Gd2O3 NCs, revealed intriguing charge storage characteristics of the NCs. Similarly, metallic NCs (gold and cobalt) and semiconducting NCs (silicon) have exhibited charge-storage characteristics when they were embedded in the gate oxide of a metal–oxide–semiconductor (MOS) structure for non-volatile memory applications.
This motivated us to explore whether films composed entirely of colloidal Gd2O3 nanocrystals could possess similar charge-storage capabilities. Charge storage in NC films arises from unpassivated surface states that can arise due to the detachment of some fraction of the surfactant molecules form the NCs’ surface during sample preparation. Thus, we employed EPD to produce films consisting only of colloidal Gd2O3 NCs to be used as the gate oxide layer in MOS architecture. We focused on capacitance-voltage (C-V) measurements of these MOS structures to characterize both the charge-storage and the dielectric properties of these films (See the Figure).
Reference Articles:
a. S.V. Mahajan and J.H. Dickerson, Dielectric properties of colloidal Gd2O3 nanocrystal films fabricated via electrophoretic deposition, Applied Physics Letters 96, 113105, 2010.
b. S.V. Mahajan and J.H. Dickerson, Understanding the growth of Eu2O3 nanocrystal films made via electrophoretic deposition, Nanotechnology 21, 145704, 2010.