MoSe2 thin films synthesized by solid state reactions between Mo and Se thin films

Abstract

Après dépôt par évaporation de fines couches superposées de molybdène et de sélénium (Mo/Se/Mo/Se... Mo), un recuit de ces structures permet l'obtention de couches minces de MoSe2. Les couches ont été caractérisées par diffraction des rayons X, spectroscopie de photoélectrons (XPS), microscopie électronique à balayage, microsonde électronique, absorption optique et par étude de l'évolution de leur résistivité en fonction de la température. On montre que, quoique les couches soient st0153chiométriques, la structure hexagonale de MoSe2 est difficile à obtenir, même après recuits à des températures de 850 K. Cependant, des couches recuites sous pression de sélénium à seulement 770 K sont bien cristallisées. La conductivité électrique est contrôlée par une conduction par sauts dans le domaine des basses températures (80-200 K) et par diffusion des porteurs au niveau des joints de grains entre 300 et 550 K.

Millimeter-scale layered MoSe2 grown on sapphire and evidence for negative magnetoresistance

“…The Mo3d peak fitting highlights a main doublet (component I) with the 3d5/2 peak located at 229.2 ± 0.1 eV binding energy, and is assigned to stoichiometric MoSe2: indeed, the energy is in agreement with the value of 229.3 eV reported for bulk MoSe2 [19]. The energy separation of 174.4 eV for the main Se3d peak is also consistent with stoichiometric MoSe2 systems [19,20]. In the Mo3d spectrum, a second, much weaker doublet, denoted as component II, is shifted by 1 eV to higher binding energies and is most likely due Mo suboxides [21].…”

Role of Mo:Na layer on the formation of MoSe2 phase in Cu(In,Ga)Se2 thin film solar cells

“…These effects were even more apparent following selenization at 848 K. The results listed in Table 2 reveal that doubling the thickness of the Mo:Na layer (from 300 nm to 700 nm) decreased the thickness of the MoSe 2 layer by more than 64% (from 1190 nm to 430 nm). Previous studies have reported that the thickness of the MoSe 2 layer at the Mo contact has a considerable influence on the performance of the resulting CIGS solar cells [11,12], particularly when this layer is excessively thick. This leaves unanswered the question of why, at a higher annealing temperature (848 K), increasing the thickness of the Mo:Na layer reduces the thickness of the MoSe 2 layer.…”

“…A specific quantity of MoSe 2 is required to ensure a good electrical contact with the back Mo contact layer [9,10]. Nonetheless, the formation of excessive MoSe 2 can lead to delamination of the film [11] with adverse effects on the V oc and FF of CIGS solar cells due to the high resistance of the MoSe 2 [12]. The production of high efficiency CIGS solar cells requires that the thickness of the MoSe 2 layer be reduced to below a particular range [13][14][15].…”

Formation of a Mo2N skin layer in columnar-structural Mo films using NH3 plasma nitridation as the Se diffusion-barrier layer

“…On the other hand, absorber growth under high temperature conditions and Se-environments causes the rapid diffusion of Se into the Mo electrode, which results in the formation of a MoSe 2 layer between the CIGS and Mo electrode. A thick MoSe 2 layer exhibits high resistivity (10 1 -10 4 Ω·cm) and volume expansion of Mo because of the formation of MoSe 2 , which can deteriorate the contact properties between CIGS and the Mo electrode [10][11][12][13][14]. Therefore, the formation of MoSe 2 is one of main reasons to decrease the efficiency of solar cells.…”