In situ ATR - FTIR spectroscopy of Hf(IV) tert butoxide adsorption on Si and Ge

2006 ◽  
Vol 917 ◽  
Author(s):  
Shilpa Dubey ◽  
Keijing Li ◽  
Harish Bhandari ◽  
Zheng Hu ◽  
C. Heath Turner ◽  
...  
Keyword(s):  
Hafnium Oxide ◽  
Density Functional ◽  
Substrate Surface ◽  
Surface Concentration ◽  
Bidentate Ligand ◽  
Initial Reaction ◽  
Process Conditions ◽  
Reaction Cell

AbstractHafnium oxide ultra thin films on Si (100) are being developed to replace thermally grown SiO2 gates in CMOS devices. In this work, a specially designed Attenuated Total Reflectance - Fourier Transform Infra Red Spectroscopy (ATR-FTIR) reaction cell has been developed to observe chemisorption of hafnium (IV) t-butoxide onto a Si and Ge ATR crystal heated up to 250°C and under 1 torr of vacuum to observe the initial reaction pathways and species on the substrate surface in real time and under typical process conditions. Chemisorption spectra were compared to spectra of the liquid precursor and to spectra generated by density functional theory (DFT) calculations of liquid, monodentate and bidentate absorbed precursor. An asymmetric stretching mode located at ~1017 cm-1 present in the chemisorbed spectra but not in the liquid spectra indicates that the adsorbed hafnium containing group is prevalent as a bidentate ligand according to calculations. Surface concentration of the chemisorbed species was dependant on the substrate temperature and precursor partial pressure allowing for determination of heats of adsorption which was 26.5 kJ/mol on Si.

scholarly journals Isolation and structure determination of missing fullerenes Gd@C 74 (CF 3 ) n through in situ trifluoromethylation

2018 ◽  
Vol 5 (9) ◽  
pp. 181015 ◽  
Author(s):  
Ayano Nakagawa ◽  
Shinobu Aoyagi ◽  
Haruka Omachi ◽  
Katsuma Ishino ◽  
Makiko Nishino ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
High Performance ◽  
Density Functional ◽  
Crystallographic Analysis ◽  
X Ray ◽  
Multi Stage ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Our trifluoromethyl functionalization method enables the dissolution and isolation of missing metallofullerenes of Gd@C 74 (CF 3 ) n . After multi-stage high-performance liquid chromatography purification, Gd@C 74 (CF 3 ) 3 and two regioisomers of Gd@C 74 (CF 3 ) are isolated. X-ray crystallographic analysis reveals that all of the isolated metallofullerenes react with CF 3 groups on pentagons of the D 3 h -symmetry C 74 cages. Highest occupied molecular orbital-lowest unoccupied molecular orbital gaps of these trifluoromethylated derivatives, estimated by absorption spectra, are in the range 0.71–1.06 eV, consistent with density functional calculations.

scholarly journals Order beyond a monolayer: the story of two 4,4’-bipyridine layers on the Sb(111) | ionic liquid interface

2022 ◽  
Author(s):  
Heigo Ers ◽  
Liis Siinor ◽  
Carolin Siimenson ◽  
Enn Lust ◽  
Piret Pikma
Keyword(s):  
Ionic Liquid ◽  
Density Functional ◽  
Electrochemical Impedance ◽  
Practical Importance ◽  
Density Functional Theory Calculations ◽  
Surface Concentration ◽  
Underlying Structure ◽  
Self Assembled Monolayer ◽  
Tunnelling Microscopy

The interface between semi-metallic Sb(111) electrode and ionic liquid with 4,4’-bipyridine addition has been studied. Using in situ scanning tunnelling microscopy and electrochemical impedance spectroscopy, the desorption of 4,4’-bipyridine was demonstrated and a dense underlying structure, formed below a sparse self-assembled monolayer, was visualized. The first SAM layer in contact with the electrode consisted of tightly packed ordered rows, which fine structure has been identified with density functional theory calculations supported by machine learning. The second SAM layer, on top of the first, is characterised by low surface concentration and its unit cell was obtained experimentally. The detection of two separate adsorbed layers indicates that the ordering of organic molecules could extend well beyond the monolayer on the electrode’s surface. These insights are of fundamental and practical importance in the development of nanoelectronic devices.

scholarly journals Эволюция проводимости и катодолюминесценции пленок оксида гафния при изменении концентрации вакансий кислорода

2018 ◽  
Vol 60 (10) ◽  
pp. 2006
Author(s):  
Д.Р. Исламов ◽  
В.А. Гриценко ◽  
В.Н. Кручинин ◽  
Е.В. Иванова ◽  
М.В. Заморянская ◽  
...  
Keyword(s):  
Refractive Index ◽  
Hafnium Oxide ◽  
Oxygen Vacancies ◽  
Trap Density ◽  
Blue Band ◽  
In Situ Method ◽  
Assisted Tunneling ◽  
Strong Scattering

AbstractThe dependence of the conductivity of the films of hafnium oxide HfO_2 synthesized in different modes is studied. Depending on the modes of synthesis, the conductivity of HfO_2 at a fixed electric field of 1.0 MV/cm changes by four orders of magnitude. It is found that the conductivity of HfO_2 is limited by the model of phonon-assisted tunneling between the traps. The thermal and optical energies of the traps W _t = 1.25 eV and W _opt = 2.5 eV, respectively, in HfO_2 are determined. It is found that the exponentially strong scattering of the conductivity of HfO_2 is due to the change in the trap density in a range of 4 × 10^19–2.5 × 10^22 cm^–3. In the cathodoluminescence spectra of HfO_2, a blue band with the energy of 2.7 eV is observed which is due to the oxygen vacancies. A correlation between the trap density and intensity of cathodoluminescence, as well as between the trap density and refractive index, is found. A nondestructive in situ method for the determination of the trap density of hafnium oxide with the use of the measurement of the refractive index is proposed. The optimum values of the concentrations of oxygen vacancies for emitting devices on the basis of the films of HfO_2 are found.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

INDIREKTE PAPIERCHROMATOGRAPHISCHE METHODE ZUR BESTIMMUNG DER HARNOESTROGENE

1961 ◽  
Vol 38 (4) ◽  
pp. 545-562 ◽  
Author(s):  
L. Kecskés ◽  
F. Mutschler ◽  
I. Glós ◽  
E. Thán ◽  
I. Farkas ◽  
...  
Keyword(s):  
Pregnant Women ◽  
Granulosa Cell ◽  
Iron Content ◽  
List Type ◽  
Granulosa Cell Tumour ◽  
Hydrolysis Of ◽  
Phenol Fraction ◽  
Qualitative Determination

ABSTRACT 1. An indirect paperchromatographic method is described for separating urinary oestrogens; this consists of the following steps: acidic hydrolysis, extraction with ether, dissociation of phenol-fractions with partition between the solvents. Previous purification of phenol fraction with the aid of paperchromatography. The elution of oestrogen containing fractions is followed by acetylation. Oestrogen acetate is isolated by re-chromatography. The chromatogram was developed after hydrolysis of the oestrogens 'in situ' on the paper. The quantity of oestrogens was determined indirectly, by means of an iron-reaction, after the elution of the iron content of the oestrogen spot, which was developed by the Jellinek-reaction. 2. The method described above is satisfactory for determining urinary oestrogen, 17β-oestradiol and oestriol, but could include 16-epioestriol and other oestrogenic metabolites. 3. The sensitivity of the method is 1.3–1.6 μg/24 hours. 4. The quantitative and qualitative determination of urinary oestrogens with the above mentioned method was performed in 50 pregnant and 9 non pregnant women, and also in 2 patients with granulosa cell tumour.

Scalability of MOCVD-deposited Hafnium Oxide

2003 ◽  
Vol 765 ◽  
Author(s):  
S. Van Elshocht ◽  
R. Carter ◽  
M. Caymax ◽  
M. Claes ◽  
T. Conard ◽  
...  
Keyword(s):  
Hafnium Oxide ◽  
Interfacial Layer ◽  
Gate Dielectric ◽  
Deposition Process ◽  
Oxide Thickness ◽  
Process Conditions ◽  
Primary Concern ◽  
Gate Electrode ◽  
K Value ◽  
High K

AbstractBecause of aggressive downscaling to increase transistor performance, the physical thickness of the SiO2 gate dielectric is rapidly approaching the limit where it will only consist of a few atomic layers. As a consequence, this will result in very high leakage currents due to direct tunneling. To allow further scaling, materials with a k-value higher than SiO2 (“high-k materials”) are explored, such that the thickness of the dielectric can be increased without degrading performance.Based on our experimental results, we discuss the potential of MOCVD-deposited HfO2 to scale to (sub)-1-nm EOTs (Equivalent Oxide Thickness). A primary concern is the interfacial layer that is formed between the Si and the HfO2, during the MOCVD deposition process, for both H-passivated and SiO2-like starting surfaces. This interfacial layer will, because of its lower k-value, significantly contribute to the EOT and reduce the benefit of the high-k material. In addition, we have experienced serious issues integrating HfO2 with a polySi gate electrode at the top interface depending on the process conditions of polySi deposition and activation anneal used. Furthermore, we have determined, based on a thickness series, the k-value for HfO2 deposited at various temperatures and found that the k-value of the HfO2 depends upon the gate electrode deposited on top (polySi or TiN).Based on our observations, the combination of MOCVD HfO2 with a polySi gate electrode will not be able to scale below the 1-nm EOT marker. The use of a metal gate however, does show promise to scale down to very low EOT values.

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