Optical thin films consisting of nanoscale laminated layers

Abstract

The control of the refractive index of laminated coatings consisting of alternating stacks of nanoscale Al2O3 and TiO2 sublayers grown by atomic layer deposition has been achieved. The refractive index of the coating linearly changed from 1.870 to 2.318 as the thickness of the single TiO2 sublayer was varied from 2.0 to 39 Å while that of the single Al2O3 sublayer was kept constant at 5.5 Å. The refractive index could be varied by adjusting only the number of growth cycles of each material. This approach will have potential applications to optical multilayer coatings consisting of well-controlled extremely thin layers.

Aluminum oxide/titanium dioxide nanolaminates grown by atomic layer deposition: Growth and mechanical properties

“…10,11 Especially Al2O3 / TiO2 nanolaminates have applications in optics, 10,19 because the Al2O3 is a low-refractive-index and the TiO2 a high-refractive-index material. 20 In mixed oxides 21 (Al2O3 and TiO2) and Al2O3 / TiO2 nanolaminates, 22 tailored optical properties varying from Al2O3 to TiO2 with gradual composition change have been demonstrated. Electrical properties 23,24 can be tuned by adjusting either the TiO2 fraction 25,26 or the bilayer thickness 27,28,29,30 or with an interfacial layers.…”

“…The first report of ATO films by combining the Me3Al and TiCl4-based processes is from year 1999 42 and several studies have been made thereafter. 20,68,69,70 At VTT, the ATO process was taken in use in mid 2000s. Overall reaction equations are:…”

Holmium and titanium oxide nanolaminates by atomic layer deposition

“…Especially important industrially are the ZrO 2 -Al 2 O 3 -ZrO 2 structures [24] used in dynamic random access memory cells. Nanolaminates may also perform as gas-diffusion barriers for reliable encapsulation of organic electronics [3], show long term durability as corrosion-protective layers [17], act as optical filters tuning the reflection from silicon substrate [11] or as hard X-ray mirrors [15]. Nanolaminates with large number of interfaces may also have reduced cross-plane thermal conductivity compared to that in chemically homogeneous films [1].…”

“…Nanolaminates of single oxides may be grown using different physical and chemical techniques, such as electron beam evaporation [13], sputtering [4], pulsed laser deposition [6] or, as apparently the most controlled method, atomic layer deposition (ALD) [1][2][3]5,7,[9][10][11][12][14][15][16][17][18][22][23][24]26]. Studies on ALD-grown nanolaminates containing rare earth oxides have so far been quite scarce [21,22], though, and none has been grown using Ti and Ho oxides as constituents.…”

Doped Sol-gel TiO2Films for Biological Applications

“…[5][6][7] It is recognized as the most efficient photocatalytic material, but, due to its large band gap energy, it can only be excited by UV irradiation. However, doping TiO 2 with transitional metals represents a promising modification method for the utilization of visible light in photocatalysis.…”