**3.3.1 ZnO and ZnO-doped layers**

Zinc oxide (ZnO) is known as one of the most multifunctional semiconductor material used in different areas for the fabrication of optoelectronic devices operating in the blue and ultra-violet (UV) region, owing to its direct wide band gap (3.37 eV) at room temperature and large exciton binding energy (60 meV) (Coleman & Jagadish, 2006). On the other hand, it is one of the most potential materials for being used as a TCO because of its high electrical conductivity and high transmission in the visible region (Fortunato et al., 2009).

Zinc oxide can be doped with various metals such as aluminium (Benouis et al., 2007) indium (Benouis et al., 2010), and gallium (Fortunato et al., 2008). The conditions of deposition and the choice of the substrate are important for the growth of the films (Benhaliliba et al., 2010). The substrate choosen must present a difference in matching lattice less than 3% to have good growth of the crystal on the substrate (Teng et al., 2007; Romeo et

A New Guide to Thermally Optimized Doped Oxides Monolayer

(b), IZO/Glass and IZO/FTO (c).

Fig. 6. Transmittance spectra, ZnO/Glass and ZnO/FTO (a), AZO/Glass and AZO/FTO

**Wavelength (nm)**

**Wavelength (nm)**

**Wavelength (nm)**

Spray-Grown Solar Cells: The Amlouk-Boubaker Optothermal Expansivity

AB 35

al., 1998). ZnO (both doped and undoped) is currently used in the copper indium gallium diselenide (CIGS, or Cu (In, Ga)Se2) thin-film solar cell (Wellings et al., 2008; Haung et al., 2002). ZnO is also promising for the application in the electronic and sensing devices, either as field effect transistors (FET), light sensor, gas and solution sensor, or biosensor.

In addition to its interesting material properties motivating research of ZnO as semiconductor, numerous applications of ZnO are well established. The world usage of ZnO in 2004 was beyond a million tons in the fields like pharmaceutical industry (antiseptic healing creams, etc.), agriculture (fertilizers, source of micronutrient zinc for plants and animals), lubricant, photocopying process and anticorrosive coating of metals.

In electronic engineering, Schottky diode are the most known ZnO-based unipolar devices. The properties of rectifying metal contacts on ZnO were studied for the first time in the late 60ties (Mead, 1965; Swank, 1966; Neville & Mead, 1970) while the rst Schottky contacts on ZnO thin lms were realized in the 80ties (Rabadanov et al., 1981; Fabricius et al., 1986).

The undoped and doped ZnO films grow with a hexagonal würtzite type structure and the calculated lattice parameters (a and c) are given in Table 1 (Benhaliliba et al. 2010).


Table 1.

Many significant differences were observed for the undoped, Al- and In-doped ZnO thin films. The films with low thickness (150 nm) have a random orientation with several peaks as reported by Wellings et al. (2008), Ramirez et al. (2007) and Abdullah et al. (2009). The same kind of growth was obtained by Tae et al. (1996) for 150 nm thick films. Whereas on FTO, the predominant ZnO film grew to a thickness of 200-300 nm as stated by Schewenzer et al. (2006). Figures (6-8) give some information about some information about ZnO and ZnO-doped layers.

al., 1998). ZnO (both doped and undoped) is currently used in the copper indium gallium diselenide (CIGS, or Cu (In, Ga)Se2) thin-film solar cell (Wellings et al., 2008; Haung et al., 2002). ZnO is also promising for the application in the electronic and sensing devices, either

In addition to its interesting material properties motivating research of ZnO as semiconductor, numerous applications of ZnO are well established. The world usage of ZnO in 2004 was beyond a million tons in the fields like pharmaceutical industry (antiseptic healing creams, etc.), agriculture (fertilizers, source of micronutrient zinc for plants and

In electronic engineering, Schottky diode are the most known ZnO-based unipolar devices. The properties of rectifying metal contacts on ZnO were studied for the first time in the late 60ties (Mead, 1965; Swank, 1966; Neville & Mead, 1970) while the rst Schottky contacts on ZnO thin lms were realized in the 80ties (Rabadanov et al., 1981; Fabricius et

The undoped and doped ZnO films grow with a hexagonal würtzite type structure and the

Many significant differences were observed for the undoped, Al- and In-doped ZnO thin films. The films with low thickness (150 nm) have a random orientation with several peaks as reported by Wellings et al. (2008), Ramirez et al. (2007) and Abdullah et al. (2009). The same kind of growth was obtained by Tae et al. (1996) for 150 nm thick films. Whereas on FTO, the predominant ZnO film grew to a thickness of 200-300 nm as stated by Schewenzer et al. (2006). Figures (6-8) give some information about some information about ZnO and ZnO-doped

**Shift (°) TC a (Å) c (Å) (c-c0)/c0(x10-5)** 




3.24 5.20

3.24 5.20

3.24 5.20

calculated lattice parameters (a and c) are given in Table 1 (Benhaliliba et al. 2010).

**Nature Grain Size (Å) Int. (%) d (Å) 2θ (°) Angle**

(100) 217 6.3 2.81 31.78 0.009 0.50

(002) 358 25.7 2.60 34.44 -0.019 2.33 (101) 254 19.4 2.47 36.24 -0.008 1.67

(100) 239 100 2.81 31.80 -0.050 2.24

(002) 211 53.5 2.60 34.42 -0.019 1.19 (101) 195 85.5 2.47 36.28 -0,028 1.95

(100) 206 70.7 2.81 31.80 -0.011 1.52

(002) 225 70.5 2.60 34.46 -0.039 1.48 (101) 195 100 2.47 36.28 -0.028 2.13

as field effect transistors (FET), light sensor, gas and solution sensor, or biosensor.

animals), lubricant, photocopying process and anticorrosive coating of metals.

al., 1986).

Undoped

IZO

AZO

Table 1.

layers.

Fig. 6. Transmittance spectra, ZnO/Glass and ZnO/FTO (a), AZO/Glass and AZO/FTO (b), IZO/Glass and IZO/FTO (c).

A New Guide to Thermally Optimized Doped Oxides Monolayer

Spray-Grown Solar Cells: The Amlouk-Boubaker Optothermal Expansivity

dashes indicate the scale (100 nm (ZnO), 1µm (AZO and IZO).

( Barsan, 1994; Goepel & Schierbaum, 1995; Ramgir et al. ,2005).

**3.3.2 SnO2:F-SnS2 gradually grown layers** 

approximated substrate temperature *T*s=440°C.

refer to tetragonal crystalline structure.

et al., Kane & Schweizer,1976).

endothermic reaction:

Fig. 8. SEM micrographs for (a) ZnO, (b) AZO and (c) IZO films, (bottom) white horizontal

Tin oxide (SnO2) is an *n*-type VI-II oxide semiconductor with a wide band gap (*E*g = 3.6 eV). Because of its good opto-electrical properties, and its ability to induce a high degree of charge compensation, it is widely used as a functional material for the optoelectronic devices, gas sensor, ion sensitive field effect transistors, and transparent coatings for organic light emitting diodes (Onyia & Okeke, 1989; Wang et al., 2006; Lee & Park, 2006; Yamada

In the last decades, pure and doped tin oxide compounds, prepared by several techniques (Manorama et al., 1999; Bruno et al., 1994; Brinzari et al., 2001; Wang et al., 2002) have been used for the preparation of high performance gas sensing and light emitting devices layers

SnO2 thin films are generally prepared using methanol CH4O: 1.0 L, demineralised water and anhydrous tin tetrachloride SnCl4. Formation of pure SnO2 is resulting from the

Approximately 0.9 µm-thick SnO2 thin films are generally deposited on glass, under an

XRD patterns of the as-grown SnO2 films are shown in Fig. 9. Diagram analysis shows that the layers present a first set of (110)-(101)-(200) X-ray diffraction peaks followed by more important pair (211)-(301). According to JCDPS 88-0287 (2000) standards, these patterns

It was reported by Yakuphanoglu (2009) and Khandelwal et al. (2009)that SnO2 films structure depends wholly on elaboration technique, substrate material and thermal treatment conditions. This feature was also discussed by Purushothaman et al. (2009) and Kim et al.

The layers present a pyramidal-clusters rough structure, which is characteristic to many Sn-

(2008) who presented temperature-dependent structure alteration of the SnO2 layers. Atomic force microscopy (AFM) 3D images of the SnO2 are presented in Fig. 10.

like metal oxides. This observation confirms the XRD results.

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Fig. 7. Photoconductivity spectra versus time of ZnO/FTO (d), AZO/FTO (e), IZO/FTO (f).

Fig. 8. SEM micrographs for (a) ZnO, (b) AZO and (c) IZO films, (bottom) white horizontal dashes indicate the scale (100 nm (ZnO), 1µm (AZO and IZO).
