tailieunhanh - Báo cáo hóa học: "Synthesis of freestanding HfO2 nanostructures"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Synthesis of freestanding HfO2 nanostructures | Kidd et al. Nanoscale Research Letters 2011 6 294 http content 6 1 294 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Synthesis of freestanding HfO2 nanostructures Timothy Kidd1 Aaron O Shea1 Kayla Boyle2 Jeff Wallace1 and Laura Strauss2 Abstract Two new methods for synthesizing nanostructured HfO2 have been developed. The first method entails exposing HfTe2 powders to air. This simple process resulted in the formation of nanometer scale crystallites of HfO2. The second method involved a two-step heating process by which macroscopic freestanding nanosheets of HfO2 were formed as a byproduct during the synthesis of HfTe2. These highly two-dimensional sheets had side lengths measuring up to several millimeters and were stable enough to be manipulated with tweezers and other instruments. The thickness of the sheets ranged from a few to a few hundred nanometers. The thinnest sheets appeared transparent when viewed in a scanning electron microscope. It was found that the presence of Mn enhanced the formation of HfO2 by exposure to ambient conditions and was necessary for the formation of the large scale nanosheets. These results present new routes to create freestanding nanostructured hafnium dioxide. PACS . Introduction Owing to its high dielectric constant and lack of reactivity with silicon hafnium dioxide has excellent characteristics for replacing SiO2 in nanometer scale applications such as gate oxides 1 2 . In addition to applications in electronics as thin films there have been reports of interesting properties of HfO2 when synthesized in the form of nanocrystals or nanorods 3-5 . Inducing dimensional constraints by reducing the size of one or more dimensions has produced emergent phenomena in a range of materials such as graphene 6 7 single layer dichalcogenides 8 and other two-dimensional systems 9 . An example for the HfO2 system was that defect concentrations are easier to .