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Preparation of nitrogen doped ZnO thin films by
colloidal route
Arnaud Valour, François Cheviré, Franck Tessier, Fabien Grasset, Stéphane
Jobic, Laurent Cario, Eric Faulques, Tengfei Jiang
To cite this version:
Arnaud Valour, François Cheviré, Franck Tessier, Fabien Grasset, Stéphane Jobic, et al.. Preparation
of nitrogen doped ZnO thin films by colloidal route. E-MRS 2015 Spring Meeting, May 2015, Lille,
France. �hal-01277164�
Preparation of nitrogen doped ZnO thin films by
colloidal route
Arnaud Valour
a), François Cheviré
a), Franck Tessier
a), Fabien Grasset
b),Stéphane Jobic
c),
Laurent Cario
c), Eric Faulques
c), Tengfei Jiang
c)a) Institut des Sciences Chimiques de Rennes (UMR CNRS 6226) – Université de Rennes 1 – France
b) Laboratory for Innovative Key Materials and Structures – National Institute of Material Science (UMI 3629 CNRS/Saint Gobain) –
Tsukuba, Japon
c) Institut des Matériaux Jean Rouxel (UMR CNRS 6502) – Université de Nantes – Nantes, France
Zinc oxide is a material of great interest exhibiting pigmental, photocatalytic, piezoelectric, antibacterial, or varistor properties that have already been developed in many different fields of industry. Still novel applications emerge in various domains but they often require the preliminary stabilization of a p-type ZnO counterpart to the natural n-type ZnO to be stimulated. In optoelectronics for instance, the high optical transparency of ZnO thin films coupled with their high electrical conductivity and their strong room temperature luminescence could indeed open up the door to revolutionary technologies as transparent electrodes in solar cells and flat panel displays, light emitting diodes, lasers, etc. We have previously reported the stabilization of p-type nitrogen doped Zn1-xO nanoparticles (ZnO:N) obtained through the decomposition of zinc peroxide (ZnO2) at low
temperature under ammonia flow. Our objective is now to extend these results to the realization of p-type ZnO thin films by colloidal route in order to achieve n-ZnO/p-ZnO:N homojonctions which would led to various applications in optoelectronics. The aim of the present work is to prepare nitrogen doped Zn1-xO thin film by thermal decomposition of ZnO2 films obtained by chemical conversion of ZnO colloidal thin films.
References:
P-type nitrogen doped ZnO nanoparticles stable under ambient conditions.
B. Chavillon, L. Cario, A. Renaud, F. Tessier, F. Cheviré, M. Boujtita, Y. Pellegrin, E. Blart, A. Smeigh, L. Hammarström, F. Odobel, S. Jobic
J. Amer. Chem. Soc. 134 (2012) 464-470
Unravelling the origin of the giant Zn deficiency in wurtzite type ZnO nanoparticles
A. Renaud; L. Cario; X. Rocquefelte; P. Deniard; E. Gautron; E. Faulques; F. Chevire, F. Tessier; S. Jobic
Scientific Reports (2015) submitted
Conclusions:
►
decomposition of ZnO2 under NH3 at T=250°C leads to Zn-poor ZnO:N. Zinc vacancy
coupled with insertion of nitrogen is necessary to access p-typeness
►
stabilization of homogeneous, regular and dense wurtzite ZnO thin film by dip-coating (thickness ≈ 200nm).►
conversion of ZnO thin film into ZnO2 by a simple chemical conversion (into H2O2
solution) in order to obtain Zn1-xO:N films by nitridation under NH3 at T=250°C
0 10 20 30 40 50 60 70 80 90 100 200 300 400 500 600 700 % T λ (nm) ZnO2 ZnO 30 32 34 36 38 40 inte nsit y ( a.u .) 2θ (°) Zn1-xO:N ZnO2 ZnO Zn(CH3COO),2H2O + 1-propanol 1/ TMAOH 2/ precipitation (ether) 3/ dispersion (EtOH) Dip-coating glass / SiO2 substrat ZnO colloidal (0.9M) Immersion of substrate Soaking (2 min) Removing the substrate (200 mm/min) heat treatment 150°C / 15 min
èThickness can be modulate by:
- Withdrawal speed
- Concentration and viscosity of the solution
► UV-Vis :
- ZnO characteristic absorption band
at 370 nm
- ZnO2 absorptionband at around 285
nm
- Zn1-xO:N with two absorption bands:
370 nm (ZnO) and around 450 nm (Nitrogen doping)
► XRD :
- 3 ZnO characteristic peaks in the
30°< 2θ < 40° area for ZnO thin film
- Conversion into H2O2 solution leads to the presence of the two less intense ZnO2 characteristic peaks - After nitridation, Zn1-xO:N thin film
with more cristallized ZnO characteristic peaks
► SEM:
- A/ regular thickness of ZnO thin film (220nm) - B/ dense and homogeneous ZnO thin film
surface with small grain size (<10nm) ZnO (wurtzite)
colloidal solution
Previous work on Zn
1-xO:N nanoparticles:
Zn5(OH)8(NO3)2(H2O)2 Δ 80°C NaOH 2 h 5 / 95 (%Vol) H2O2 / H2O Zn(NO3)2,6H2O Nitridation (NH3) Δ 250°C 30 min Precursor ZnO2 (pyrite structure) Zn1-xO:N (wurtzite) 20 40 60 80 In tensité (u. a.) 2theta (°) ZnO2 ZnO (air 250°C) ZnO:N (NH3 250°C)
ZnO thin film synthesis by dip-coating:
XRD:
(on samples with thickness ≈ 220nm, SiO2 substrate)UV-Vis spectroscopy:
(on samples with thickness ≈ 220nm, SiO2 substrate)- XRD: ZnO-wurtzite structure type - Salmon color è nitrogen insertion - Material with up to 20% Zn vacancies - P-type conductivity stable over more
than 2 years
Electrochemical (Mott-Schottky) and photoelectrochemical characterization of ZnO:N prepared at 250°C (blue ellipse), 550°C
(red ellipse), and ZnO-ref (gray ellipse). The comparison with the ternary phase diagram reporting the compositions of all compounds suggests that ZnO poor nitrogen-doped samples are p-type while Zn-rich samples are n-type (on = under illumination, off = in the dark).
SEM
ZnO thin film conversion into ZnO
2and Zn
1-xO:N :
ZnO
thin filmZnO
2 thin filmZn
1-xO:N
thin film (slightlyorange) Chemical conversion H2O2 / H2O (5/35 mL) Nitridation under NH3 Δ 250°C 30 min Zn1-xO:N SiO2 substrateA
B
(10 0) (00 2) (10 1) (1 1 1) (20 0) ≈ 200nm ► SEM:- variation of the thickness after conversion in H2O2 solution and nitridation
- dense and homogeneous surface with increased of grain size after conversion (H2O2)
(SEM images of ZnO converted thin films, glass substrate)
