The microwave characterization of single crystal lithium and calcium fluoride at cryogenic temperatures

Hartnett, John G.; Fowler, Alison; Tobar, Michael E.; Křupka, J.

doi:10.1109/tuffc.2004.1295423

Cited by 12 publications

(6 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The dielectric constant of CaF 2 synthesized by the Bridgman method 61 was experimentally characterized using the Whispering-Gallery mode method, 62 and values of 6.844 and 6.502 were obtained at temperatures of 296 K and 4.9 K, respectively (using a frequency of 17.5 GHz). 63 This value is similar to that obtained when analyzing CaF 2 crystals synthesized by the Kyropoulos method 61 using a conventional capacity bridge-measuring system, 64,65 which leads to a dielectric constant of $6.8 at 25 C. In the past (i.e., in 1938), experimental values up to $8.43 at 25 C had been reported, 66 although details on the synthesis and measuring method were not disclosed. Although traditionally this value (8.43) has been amply cited in the literature, 64,67,68 we consider $6.8 to be more valid due to the better defined synthesis and measuring methods employed in Refs.…”

Section: Fundamental Electrical Propertiessupporting

confidence: 65%

Calcium fluoride as high-k dielectric for 2D electronics

Wen

Lanza

2021

Applied Physics Reviews

View full text Add to dashboard Cite

Calcium fluoride is a dielectric material with a wide bandgap ($12.1 eV) and a relatively high dielectric constant ($6.8) that forms a van der Waals interface with two-dimensional (2D) materials, meaning that it contains a very low amount of defects. Thin calcium fluoride films can be synthesized using multiple techniques that are scalable to the wafer level, including molecular beam epitaxy, atomic layer deposition, and chemical vapor deposition. However, the consolidation of calcium fluoride as dielectric for 2D electronics requires overcoming some fundamental challenges related to material quality and integration, as well as carrying out advanced characterization and computational studies to evaluate its real potential. Here, we review the status of calcium fluoride dielectric films in terms of material synthesis, fundamental electrical properties, and future applications; we also discuss the most important challenges of calcium fluoride integration in 2D materials-based, solid-state nano/micro-electronic devices, and propose several potential routes to overcome them. Our manuscript may serve as a useful guide for other scientists working on 2D electronics in general, and provides a clear pathway for calcium fluoride research in the future.

show abstract

Section: Fundamental Electrical Propertiessupporting

confidence: 65%

Calcium fluoride as high-k dielectric for 2D electronics

Wen

Lanza

2021

Applied Physics Reviews

View full text Add to dashboard Cite

show abstract

“…As a promising alternative to amorphous oxides and hBN, here we use for the first time 2 nm thick epitaxial calcium fluoride (fluorite, CaF 2 ) as a gate insulator in scalable GFETs with a graphene channel grown by chemical vapour deposition (CVD) and transferred onto the CaF 2 substrate. CaF 2 is an ionic crystalline insulator with good dielectric properties (E g = 12.1 eV, ε in range between 6.8 16 and 8.43 17 ) which forms quasi van der Waals interfaces with 2D materials 18 and at the same time can be epitaxially grown on Si(111) at 250 o C 19 in line with CMOS thermal budget requirements. This, in particular, makes CaF 2 an attractive candidate for the gate insulator of 2D FETs, even more so as CaF 2 allows the heteroepitaxy of 2D semiconductors on CaF 2 (111), as already confirmed for MoSe 2 20 and MoTe 2 .…”

mentioning

confidence: 99%

Reliability of scalable MoS₂ FETs with 2 nm crystalline CaF₂ insulators

et al. 2019

View full text Add to dashboard Cite

Graphene is a promising material for applications as a channel in graphene fieldeffect transistors (GFETs) which may be used as a building block for optoelectronics, high-frequency devices and sensors. However, these devices require gate insulators which ideally should form atomically flat interfaces with graphene and at the same time contain small densities of traps to maintain high device stability. Previously used amorphous oxides, such as SiO 2 and Al 2 O 3 , however, typically suffer from oxide

show abstract

“…Employing “dielectric resonator” techniques (using the whispering gallery and quasi-

modes) several low loss single-crystal dielectrics have been measured [ 38 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ]. In Table 1 , results of room temperature permittivity and the thermal coefficient of permittivity measurements using these techniques for several single-crystal dielectrics are presented.…”

Section: Microwave Measurements Of Dielectricsmentioning

confidence: 99%

Microwave Measurements of Electromagnetic Properties of Materials

Křupka

2021

Materials

View full text Add to dashboard Cite

A review of measurement methods of the basic electromagnetic parameters of materials at microwave frequencies is presented. Materials under study include dielectrics, semiconductors, conductors, superconductors, and ferrites. Measurement methods of the complex permittivity, the complex permeability tensor, and the complex conductivity and related parameters, such as resistivity, the sheet resistance, and the ferromagnetic linewidth are considered. For dielectrics and ferrites, the knowledge of their complex permittivity and the complex permeability at microwave frequencies is of practical interest. Microwave measurements allow contactless measurements of their resistivity, conductivity, and sheet resistance. These days contactless conductivity measurements have become more and more important, due to the progress in materials technology and the development of new materials intended for the electronic industry such as graphene, GaN, and SiC. Some of these materials, such as GaN and SiC are not measurable with the four-point probe technique, even if they are conducting. Measurement fixtures that are described in this paper include sections of transmission lines, resonance cavities, and dielectric resonators.

show abstract

The microwave characterization of single crystal lithium and calcium fluoride at cryogenic temperatures

Cited by 12 publications

References 15 publications

Calcium fluoride as high-k dielectric for 2D electronics

Calcium fluoride as high-k dielectric for 2D electronics

Reliability of scalable MoS₂ FETs with 2 nm crystalline CaF₂ insulators

Microwave Measurements of Electromagnetic Properties of Materials

Contact Info

Product

Resources

About

The microwave characterization of single crystal lithium and calcium fluoride at cryogenic temperatures

Cited by 12 publications

References 15 publications

Calcium fluoride as high-k dielectric for 2D electronics

Calcium fluoride as high-k dielectric for 2D electronics

Reliability of scalable MoS2 FETs with 2 nm crystalline CaF2 insulators

Microwave Measurements of Electromagnetic Properties of Materials

Contact Info

Product

Resources

About

Reliability of scalable MoS₂ FETs with 2 nm crystalline CaF₂ insulators