Determination of the molecular size of growth species in the AP-MOCVD of ZnO from DEZ and H2O

Study of the thermal decomposition of “captured” intermediates in the CVD of ZnO from DEZ and H2O by TGA–DTA and quadrupole mass spectroscopy

“…The reaction of DEZ with water is known to produce either ethylzinc hydroxide (C 2 H 5 ZnOH) or zinc hydroxide {Zn(OH) 2 Our previous study [7] revealed that the gaseous intermediate in the CVD of ZnO is mainly composed of small clusters (possibly tetramers) when the reactor temperature is in the range of 400À600 1C and larger clusters of up to 20 molecules at 700 1C (Fig. 4).…”

“…Diethylzinc (Zn(C 2 H 5 ) 2 ), (DEZ), is commonly used as Zn source due to its high vapor pressure. Various oxygen sources have been used such as oxygen (O 2 ) [4,5], water (H 2 O) [6][7][8][9], carbon dioxide (CO 2 ) [10,11], alcohols [12], and nitrous oxide (N 2 O) [13]. The oxygen source should largely affect the quality of the grown ZnO film, but it is yet unclear as to which is the optimum choice.…”

“…It is important, therefore, to understand the growth processes in each of these chemical vapor deposition (CVD) systems. We recently reported the molecular sizes [7] and sticking probabilities [8] of the intermediate species as a function of temperature in the MOCVD of ZnO from DEZ and H 2 O. In this paper, we use simultaneous thermogravimetric analysis-differential thermal analysis (TGA-DTA) and quadrupole mass spectrometry (QMS) to analyze the intermediates in the reaction of DEZ with H 2 O.…”

Atmospheric pressure chemical vapor deposition mechanism of Al2O3 film from AlCl3 and O2

“…The linearity of the semi-logarithmic plot supports this assumption. The relation of the slope (a) of the semi-log plots with the tube diameter (d) can be used to identify the rate-limiting step [18][19][20][21][22]. For example, in Fig.…”

“…Association reactions of the intermediates yield clusters that diffuse to the substrate surface to form the film or serve as nucleus for the formation of particles [23,24]. The Chapman-Enskog equation can be used to estimate the collision diameter or molecular size of the diffusing gaseous species if the diffusivities are known [18][19][20][21][22]25]. Since we have a three-component system involving AlCl 3 , Ar, and O 2 , we employ the Stefan-Maxwell equation [26] in our calculations.…”