Supporting Information for Low Temperature Epitaxial Oxide Ultrathin ...
Supporting Information for Low Temperature Epitaxial Oxide Ultrathin Films by Atomic Layer Deposition Mariona Coll,†,* Jaume Gazquez,†,‡ Anna Palau,† Maria Varela, ‡, § Xavier Obradors,† Teresa Puig† †Institut
de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 32831, United States § Departamento de Física Aplicada III, Universidad Complutense de Madrid, Madrid, 28040, Spain ‡
THERMOGRAVIMETRIC ANALYSIS
Thermal analysis were performed at atmospheric pressure under nitrogen gas in order to investigate the decomposition behaviour of Ce(thd)4 precursor. Figure SI .1 shows the TGA (in black) and DTA (in red) thermograms. From the thermogravimetric analysis (TGA) it observed that the main weight loss (90.6%) occurs between 1 220ºC and 300ºC and beyond 300ºC the Ce(thd)4 is completely decomposed in accordance with reference data. Figure SI.1 TGA (in black) and DTA (in red) measurements of Ce(thd)4 ALD powder precursor.
ALD GROWTH CHARACTERISTICS
To evaluate the ALD conditions for CeO2 deposition, substrate temperature and Ce(thd)4 pulse have been varied, see Figure SI.2. YSZ substrate temperature was varied from 200ºC to 290ºC and the growth per cycle remained constant indicating the potential ALD window. The thickness dependence on the Ce(thd)4 pulse was in2 vestigated at 275ºC and the ozone pulse was kept constant at 2.5 s based on previous work. Based on these results it is observed that saturated surface reaction is reached up to 1 s Ce(thd)4 pulse time.
Figure SI.2 Growth per cycle dependence on the (a) YSZ substrate (400 cycles) using Ce(thd)4 of 2 s. (b) Ce(thd)4 pulse length at 275ºC.
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POST-THERMAL TREATMENT OF ALD-CEO2
The evolution of ALD-CeO2 film quality after post-thermal treatment at 900ºC for 15 min has been discussed in ultrathin films (3 nm) in the main text. Dewetting phenomena have been identified from both AFM and STEM analysis and attributed to post-treatment time and/or film thickness. Shorter post-processing treatments and thicker films have been studied by x-ray diffraction and atomic force microscopy, see Figure SI.3 and SI.4. Ultrathin films (3 nm) exposed to shorter post-processing time (5 min) at 900ºC lead to (00l) CeO2 films, see Figure SI.3(a), similar to what was observed for 15 min processing (Figure 1). When thicker samples (12 nm) are exposed at 900ºC for 15 min, more intense (00l) CeO2 reflections are observed, see Figure SI.3 (b), as expected from the presence of larger amount of CeO2.
Figure SI.3 XRD θ-2θ scans of (a) 3 nm ALD-CeO2 film on YSZ post-treated at 900ºC for 5 min in oxygen and (b) 12 nm ALD-CeO2 film on YSZ post-treated at 900ºC for 15 min in oxygen. AFM analysis from these samples show uniform, continuous and smooth (rms
de Ciencia de Materials de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra, Spain Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 32831, United States § Departamento de Física Aplicada III, Universidad Complutense de Madrid, Madrid, 28040, Spain ‡
THERMOGRAVIMETRIC ANALYSIS
Thermal analysis were performed at atmospheric pressure under nitrogen gas in order to investigate the decomposition behaviour of Ce(thd)4 precursor. Figure SI .1 shows the TGA (in black) and DTA (in red) thermograms. From the thermogravimetric analysis (TGA) it observed that the main weight loss (90.6%) occurs between 1 220ºC and 300ºC and beyond 300ºC the Ce(thd)4 is completely decomposed in accordance with reference data. Figure SI.1 TGA (in black) and DTA (in red) measurements of Ce(thd)4 ALD powder precursor.
ALD GROWTH CHARACTERISTICS
To evaluate the ALD conditions for CeO2 deposition, substrate temperature and Ce(thd)4 pulse have been varied, see Figure SI.2. YSZ substrate temperature was varied from 200ºC to 290ºC and the growth per cycle remained constant indicating the potential ALD window. The thickness dependence on the Ce(thd)4 pulse was in2 vestigated at 275ºC and the ozone pulse was kept constant at 2.5 s based on previous work. Based on these results it is observed that saturated surface reaction is reached up to 1 s Ce(thd)4 pulse time.
Figure SI.2 Growth per cycle dependence on the (a) YSZ substrate (400 cycles) using Ce(thd)4 of 2 s. (b) Ce(thd)4 pulse length at 275ºC.
1
POST-THERMAL TREATMENT OF ALD-CEO2
The evolution of ALD-CeO2 film quality after post-thermal treatment at 900ºC for 15 min has been discussed in ultrathin films (3 nm) in the main text. Dewetting phenomena have been identified from both AFM and STEM analysis and attributed to post-treatment time and/or film thickness. Shorter post-processing treatments and thicker films have been studied by x-ray diffraction and atomic force microscopy, see Figure SI.3 and SI.4. Ultrathin films (3 nm) exposed to shorter post-processing time (5 min) at 900ºC lead to (00l) CeO2 films, see Figure SI.3(a), similar to what was observed for 15 min processing (Figure 1). When thicker samples (12 nm) are exposed at 900ºC for 15 min, more intense (00l) CeO2 reflections are observed, see Figure SI.3 (b), as expected from the presence of larger amount of CeO2.
Figure SI.3 XRD θ-2θ scans of (a) 3 nm ALD-CeO2 film on YSZ post-treated at 900ºC for 5 min in oxygen and (b) 12 nm ALD-CeO2 film on YSZ post-treated at 900ºC for 15 min in oxygen. AFM analysis from these samples show uniform, continuous and smooth (rms
