Decrease Of Deposition Pressure Research Articles

Effect of physical densification on sub-gap density of states in amorphous InGaZnO thin films

In this study, we investigate the relationship between the physical densification and sub-gap density-of-states (DOS) distribution of a-IGZO films prepared under various deposition pressures. For TFTs with a-IGZO channel films, the field effect mobility increases from 10.9 to 24.8 cm2/V·s, and the on-current increases from 1.5 to 20.8 μA as the deposition pressure for the channel films decreases from 7 to 1 mTorr. The sub-gap DOS distributions obtained from the electrical characteristics indicate the changes in the density of accepter-like tail states with deposition pressure. Further, the physical densification of the channel films increases as the deposition pressure decreases. Our study demonstrates that the lower density of accepter-like tail states and the higher physical densification contribute to the improved performance of a-IGZO TFTs.

Preparation and optimization of a molybdenum electrode for CIGS solar cells

Molybdenum (Mo) films were deposited by radio frequency (RF), direct current (DC) and mixed magnetron sputtering, respectively. With changing the deposition parameters including deposition pressure and power, the films show different surface morphology and crystallinity. Lower resistivity of the films is obtained in the DC mode and better reflectivity of the films is obtained in the RF mode. It is shown that the crystallinity increases when the deposition pressure decreases. The crystallinity and the grain size both increase as the deposition power increasing. The lowest resistivity of the single Mo film is 34×10-6 Ω·cm when the deposition pressure is 0.1 Pa and the deposition power is 300 W in the DC mode. In order to obtain lower resistivity, better adhesion and better reflectivity, bilayer films and tri-layer films were both deposited in different mode. They all show good adhesion and low resistivity. The Mo films deposited in mixed mode show better reflectivity. It is demonstrated that the resistivity of about 65×10-6 Ω·cm is achieved in DC/RF mode and the resistivity of about 61×10-6 Ω·cm is achieved in RF/DC/RF mode. And the tri-layer films achieved in RF/DC/RF mode have better reflectivity than bilayer films achieved in DC/RF mode. The tri-layer films achieved in RF/DC/RF mode is appropriate for using as the electrode of CIGS solar cells.

Improving the uncommon (110) growing orientation of Al-doped ZnO thin films through sequential pulsed laser deposition

High quality Al-doped ZnO (AZO) films with uncommon (110) orientation are obtained on amorphous substrate by using Sequential Pulsed Laser Deposition technique. The dependence of the structural, optical and electrical properties with dopant concentration and oxygen deposition pressure was investigated systematically. We note a transition from the (002) preferential orientation of crystallites to an uncommon (110) orientation due to a combined effect of doping concentration and deposition pressure decreasing. For constant deposition pressure of 5Pa the film crystallinity is changed from preferential (002) to polycrystalline when increasing dopant concentration. For the maximum dopant concentration that we have investigated (i.e., 4.4% at.) structural properties of AZO films are changed from a polycrystalline phase to a (110) preferential orientation when the deposition pressure decreases. This uncommon growth mode is accompanied by a change of the morphology from a densely packed granular structure to a more rarefied one. Moreover, the band gap widens up to 3.88eV and the electrical resistivity drops to 5.4×10−2Ωcm. The structural changes were attributed to two mechanisms: a first one, responsible for the (002) phase suppression as a consequence of aluminum ion bombardment during the doping process and, a second one, in charge with (110) phase growth as the diffusion rates of zinc and oxygen atoms are affected by the dopant incorporation and by the decrease of deposition pressure.

Effect of deposition pressure on the dielectric properties of bismuth magnesium niobium titanium thin films prepared by RF magnetron sputtering

The Bi1.5Mg0.5Nb0.5Ti1.5O7 (BMNT) thin films with cubic pyrochlore structure were prepared on Pt/TiOx/SiO2/Si substrates by rf magnetron sputtering. The effects of deposition pressure on the structure and dielectric properties of BMNT thin films were investigated. As the deposition pressure decreases, the crystallinity becomes better, and the dielectric properties and tunability have an obvious improvement. The BMNT thin film deposited at 1Pa exhibited a dielectric constant of 107.86, a tunability of 30.0% at 1MV/cm, low tangent loss of 0.0017, and the largest FOM of 176.47. The excellent dielectric properties make BMNT thin films promising for potential tunable capacitor applications.

Influences of arc current on composition and properties of MgO thin films prepared by cathodic vacuum arc deposition

MgO thin films with high optical transmittances (more than 90%) were prepared by cathodic vacuum arc deposition technique. With the increase of arc current from 40 to 80 A, the deposition pressure decreases and the film thickness increases; the atomic ratio of Mg/O in MgO thin films (obtained by RBS) increases from 0.97 to 1.17, giving that deposited at 50 A most close to the stoichiometric composition of the bulk MgO; the grains of MgO thin films grow gradually as shown in SEM images. XRD patterns show that MgO (1 1 0) orientation is predominant for films prepared at the arc currents ranged from 50 to 70 A. The MgO (1 0 0) orientation is much enhanced and comparable to that of MgO (1 1 0) for films prepared at the arc current of 80 A. The secondary electron emission coefficient of MgO thin film increases with arc current ranged from 50 to 70 A.

Effects of plasma power and deposition pressure on the properties of the low dielectric constant plasma polymerized cyclohexane thin films deposited by plasma enhanced chemical vapor deposition

Effects of plasma power and deposition pressure on the properties of low dielectric constant plasma polymerized cyclohexane (PPCHex) thin films deposited by plasma enhanced chemical vapor deposition were investigated. As plasma power increased, the relative dielectric constant (k) value increased, while the C-H bonding concentration decreased. Unlike the power, as deposition pressure increased, k value decreased and the C-H bonding concentration increased. Increase of plasma power could be considered to be quite similar to decrease of deposition pressure. The PPCHex thin films with higher k values had smaller intensities of C-H bonding concentrations and higher thermal stability. Copper diffusion into the PPCHex thin films was also investigated by current-voltage measurement and transmission electron microsopy. PPCHex thin films were resistant to Cu diffusion up to 400°C, while there was a notable amount of Cu diffused into the PPCHex thin films after 450°C annealing.