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A low temperatures between 120 <sup>o</sup>C and 150 <sup>o</sup>C an amorphous TiO<sub>2</sub> layer is grown in the ALD, and at higher temperatures between 300 <sup>o</sup>C and 350 <sup>o</sup>C an anatase TiO<sub>2</sub> layer is grown. At temperatures between 150 <sup>o</sup>C and 300 <sup>o</sup>C the TiO<sub>2</sub> layer will be a mixture of both amorphous and anatase TiO<sub>2</sub>.
A low temperatures between 120 <sup>o</sup>C and 150 <sup>o</sup>C an amorphous TiO<sub>2</sub> layer is grown in the ALD, and at higher temperatures between 300 <sup>o</sup>C and 350 <sup>o</sup>C an anatase TiO<sub>2</sub> layer is grown. At temperatures between 150 <sup>o</sup>C and 300 <sup>o</sup>C the TiO<sub>2</sub> layer will be a mixture of both amorphous and anatase TiO<sub>2</sub>.


For Si wafers, anatase TiO<sub>2</sub> is best grown on wafers without native oxide (removed using BHF), and amorphous TiO<sub>2</sub> is best grown on wafers with native oxide.
For Si wafers, amorphous TiO<sub>2</sub> is best grown on wafers with native oxide, and anatase TiO<sub>2</sub> is best grown on wafers without native oxide (removed using HF).


===TiO<sub>2</sub> standard recipe===
===TiO<sub>2</sub> standard recipe===
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===TiO<sub>2</sub> deposition rates===
===TiO<sub>2</sub> deposition rates===


In the graphs below the TiO<sub>2</sub> thickness as function of the number of cycles for deposition temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C can be seen. From the equations the number of cycles required for a certain thickess can be calculated. All result have been obtained for Si wafers with native oxide.   
In the graphs below the TiO<sub>2</sub> thickness as function of the number of cycles for deposition temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C can be seen. From the equations the number of cycles required for a certain thickess to be deposited can be calculated. All results have been obtained for Si wafers with native oxide.   


<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="300px" heights="300px" perrow="3">
<gallery caption="Titanium dioxide thickness as function of number of cycles" widths="300px" heights="300px" perrow="3">
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===TiO<sub>2</sub> results===
===TiO<sub>2</sub> results===


Some some SEM images of TiO<sub>2</sub> deposited on a Si surface at different temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C are shown below. Some of samples have been treated with HF (hydrofluoric acid) to remove the native oxide layer silicon samples just before the ALD deposition.
Some some SEM images of TiO<sub>2</sub> deposited on a Si surface at different temperatures between 150 <sup>o</sup>C and 350 <sup>o</sup>C are shown below. Some of samples have been treated with HF (hydrofluoric acid) to remove the native oxide layer just before the ALD deposition.


<gallery caption="Titanium dioxide deposited at different temperatures on a Si surface" widths="250px" heights="250px" perrow="3">
<gallery caption="Titanium dioxide deposited at different temperatures on a Si surface" widths="250px" heights="180px" perrow="3">
image:TiO2 150C 1200 cycles Si_HF_treated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles, HF treated.
image:TiO2 150C 1200 cycles Si_HF_treated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles, HF treated.
image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles.
image:TiO2 150C 1200 cycles Si_untreated.jpg| Temperature 150 <sup>o</sup>C, 1200 cycles.
image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature 250 <sup>o</sup>C, 750 cycles.
image:TiO2 250C 750cycles_Si_untreated.jpg| Temperature 250 <sup>o</sup>C, 750 cycles.
</gallery>
</gallery>
<gallery caption="" widths="250px" heights="250px" perrow="5">
<gallery caption="" widths="250px" heights="180px" perrow="5">
image:TiO2 1000 cycles 300C Si_HF.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles, HF treated.
image:TiO2 1000 cycles 300C Si_HF.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles, HF treated.
image:TiO2 1000 cycles 300C Si_un.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles.
image:TiO2 1000 cycles 300C Si_un.jpg| Temperature 300 <sup>o</sup>C, 1000 cycles.
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</gallery>
</gallery>


Below some SEM images of anatase TiO<sub>2</sub> deposited at 120 <sup>o</sup>C on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO<sub>2</sub> layer of about 25 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  
Below some SEM images of amorphous TiO<sub>2</sub> deposited at 120 <sup>o</sup>C on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO<sub>2</sub> layer of about 25 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  


<gallery caption="Anatase titanium dioxide deposited on Si trenches" widths="250px" heights="250px" perrow="3">
<gallery caption="Amorphous titanium dioxide deposited on Si trenches" widths="250px" heights="180px" perrow="3">
image:SEM-TiO2-120C-1.jpg|
image:SEM-TiO2-120C-1.jpg|
image:SEM-TiO2-120C-2.jpg|
image:SEM-TiO2-120C-2.jpg|
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</gallery>
</gallery>


Below some SEM images of amorphous TiO<sub>2</sub> deposited at 300 <sup>o</sup>C on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO<sub>2</sub> layer of about 26 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  
Below some SEM images of anatase TiO<sub>2</sub> deposited at 300 <sup>o</sup>C on Si trenches are shown. The width of the trenches is 200 nm, and the depth is 4 µm, i.e. the aspect ratio is 1:20. The number of cycles is 500, and this results in a TiO<sub>2</sub> layer of about 26 nm. From the SEM images it is seen that the TiO<sub>2</sub> layer covers the trenches very well.  


<gallery caption="Amorphous titanium dioxide deposited on Si trenches" widths="250px" heights="250px" perrow="3">
<gallery caption="Anastase titanium dioxide deposited on Si trenches" widths="250px" heights="180px" perrow="3">
image:TiO2 trenches-300C-1.jpg|
image:TiO2 trenches-300C-1.jpg|
image:TiO2 trenches-300C-2.jpg|
image:TiO2 trenches-300C-2.jpg|
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XPS measurements of TiO<sub>2</sub> deposited at 120 <sup>o</sup>C and 300 <sup>o</sup>C are shown below. From the XPS measurements it can be calculated that at temperaturs below 120 <sup>o</sup>C the TiO<sub>2</sub> layer will be contaminated with about 1-3 % chlorine molecules from the TiCl<sub>4</sub> precursor. This can be also seen as small white dots in SEM images of the anatase TiO<sub>2</sub> layers above.
XPS measurements of TiO<sub>2</sub> deposited at 120 <sup>o</sup>C and 300 <sup>o</sup>C are shown below. From the XPS measurements it can be calculated that at temperaturs below 120 <sup>o</sup>C the TiO<sub>2</sub> layer will be contaminated with about 1-3 % chlorine molecules from the TiCl<sub>4</sub> precursor. This can be also seen as small white dots in SEM images of the anatase TiO<sub>2</sub> layers above.


[[image:XPS_TiO2.jpg|320x320px|left|thumb|XPS measurements of titanium dioxide]]
[[image:XPS_TiO2.jpg|320x320px|left|thumb|XPS measurements of titanium dioxide.]]




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