Spatial structure of radio frequency ring-shaped magnetized discharge sputtering plasma using two facing ZnO/Al2O3 cylindrical targets for Al-doped ZnO thin film preparation

Abstract

Spatial structure of high-density radio frequency ring-shaped magnetized discharge plasma sputtering with two facing ZnO/Al2O3 cylindrical targets mounted in ring-shaped hollow cathode has been measured and Al-doped ZnO (AZO) thin film is deposited without substrate heating. The plasma density has a peak at ring-shaped hollow trench near the cathode. The radial profile becomes uniform with increasing the distance from the target cathode. A low ion current flowing to the substrate of 0.19 mA/cm2 is attained. Large area AZO films with a resistivity of 4.1 – 6.7×10-4 Ω cm can be prepared at a substrate room temperature. The transmittance is 84.5 % in a visible region. The surface roughnesses of AZO films are 0.86, 0.68, 0.64, 1.7 nm at radial positions of r = 0, 15, 30, 40 mm, respectively, while diffraction peak of AZO films is 34.26°. The grains exhibit a preferential orientation along (002) axis.

Spatial profile of Al-ZnO thin film on polycarbonate deposited by ring-shaped magnetized rf plasma sputtering with two facing cylindrical Al2O3 – ZnO targets

“…36,37) It is found that the radial profile for z = 10 mm has a peak of approximately 0.1 mA at r = 45 mm positioned at the center of the hollow groove. The plasma density n i for I is = 0.1 mA is estimated to be 7 × 10 10 cm −3 with the assumption of an electron temperature of T e = 46400 K 30) based on…”

“…The retentivity and the coercive force of the neodymium material are 12700 G and −11500 Oe, respectively. Figure 3 30) shows the 2D magnetic flux lines around the hollow groove. It is found that the magnetic field lines close the outlet of the groove so that electrons are confined in the hollow trench.…”

“…Aluminum-doped zinc oxide (AZO) has been investigated as a candidate for such alternative materials for ITO, because ZnO is abundantly available and has attractive characteristics such as the non-toxicity and low cost. In general, AZO films have been prepared by a magnetron plasma sputtering [2][3][4][5][6][7][8][9][10][11][12][13][14][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] because a high-quality and highdeposition rate are attained. However, the resistivity of AZO films deposited by DC magnetron sputtering has exhibited a significant spatial distribution at lower substrate temperature below 300 °C10) It has been reported that the area of high resistivity is correlated to the target erosion pattern, that is, the closed E × B drifted high-density plasma, where E and B are the electric field and magnetic flux density, respectively.…”

“…In our previous work, 30) a ring-shaped magnetized rf plasma sputtering process with two facing cylindrical AZO targets was used to deposit the AZO films on a glass substrate under the room-substrate-temperature for solving this problem. It has been reported that the large area AZO films with a resistivity of 4.1-6.7 × 10 −4 Ω • cm and a transmittance of 84.5% in the visible range can be prepared by the novel sputtering system.…”

Synthesis of Al-Doped ZnO Films Assisted with Hollow-Cathode Glow Discharge and Their Characterization

“…They found that hollow-cathode sputtering can be utilized to deposit AZO films for solar cell applications. Sumiyama et al 42 used radiofrequency (RF) ring-shaped magnetized discharge plasma sputtering to deposit AZO thin films and reported that this technique could produce AZO films with high transmittance. Although these sputtering systems produced good results, in these systems, metallic targets with specific dimensions and compositions are required to deposit any material.…”