scholarly journals Determination of the vapour pressure curves and vaporization enthalpies of hafnium alkoxides using thermogravimetric analysis

2019 ◽  
Vol 6 (1) ◽  
pp. 181193 ◽  
Author(s):  
Changhong Wang ◽  
Shenghai Yang ◽  
Yongming Chen

In order to identify a volatile metallo-organic precursor for the deposition of hafnium oxide (HfO 2 ) films for atomic layer deposition (ALD) applications, the evaporative properties of hafnium alkoxides (hafnium isopropoxide, hafnium n -propoxide and hafnium n -butoxide) were investigated using thermogravimetric analysis. These hafnium alkoxide samples were synthesized by the electrochemical method and characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance and inductively coupled plasma analysis techniques. The characterization results indicated that the products were 99.997% high-purity hafnium alkoxides and could meet the requirement of purity considering the usage of making HfO 2 gate oxide by ALD. Synthesized samples were subjected to a simultaneous thermogravimetric–differential thermal analysis unit at 10 K min −1 in a dry nitrogen atmosphere flowing at 100 ml min −1 . Benzoic acid was used to calculate a calibration constant, which could then be inserted into a modified Langmuir equation to calculate vapour pressure curves for hafnium isopropoxide and hafnium n -propoxide. Detailed vapour pressure data for the HfO 2 precursor hafnium alkoxides were determined. The vapour pressure curve of hafnium isopropoxide was constructed within the first stage, and calculated to be ln p = 31.157 (±0.200)−13130.57 (±56.50)/T. Hafnium n -propoxide and hafnium n -butoxide were simultaneously undergoing evaporation and decomposition, thus making calculations invalid.

2018 ◽  
Vol 9 ◽  
pp. 1895-1905 ◽  
Author(s):  
André Giese ◽  
Sebastian Schipporeit ◽  
Volker Buck ◽  
Nicolas Wöhrl

In this work, the deposition of carbon nanowalls (CNWs) by inductively coupled plasma enhanced chemical vapor deposition (ICP-PECVD) is investigated. The CNWs are electrically conducting and show a large specific surface area, which is a key characteristic to make them interesting for sensors, catalytic applications or energy-storage systems. It was recently discovered that CNW films can be deposited by the use of the single-source metal-organic precursor aluminium acetylacetonate. This precursor is relatively unknown in combination with the ICP-PECVD deposition method in literature and, thus, based on our previous publication is further investigated in this work to better understand the influence of the various deposition parameters on the growth. Silicon, stainless steel, nickel and copper are used as substrate materials. The CNWs deposited are characterized by scanning electron microscopy (SEM), Raman spectroscopy and Auger electron spectroscopy (AES). The combination of bias voltage, the temperature of the substrate and the substrate material had a strong influence on the morphology of the graphitic carbon nanowall structures. With regard to these results, a first growth model for the deposition of CNWs by ICP-PECVD and aluminium acetylacetonate is proposed. This model explains the formation of four different morphologies (nanorods as well as thorny, straight and curled CNWs) by taking the surface diffusion into account. The surface diffusion depends on the particle energies and the substrate material and thus explains the influence of these parameters.


Author(s):  
K. Srinivasan

There exists a maximum in the products of the saturation properties such as


1981 ◽  
Vol 46 (10) ◽  
pp. 2446-2454
Author(s):  
Václav Svoboda ◽  
Zdeněk Wagner ◽  
Petr Voňka ◽  
Jiří Pick

A method of calculating the heat capacity difference of liquid and its vapour along saturated vapour pressure curve is discussed. The qualitative course of this difference in dependence on temperature obtained from the data on the temperature dependence of heat of vaporization of pure substances is judged.


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