Negative-ion bombardment increases during low-pressure sputtering deposition and their effects on the crystallinities and piezoelectric properties of scandium aluminum nitride films

2021 ◽  
Author(s):  
Takumi Tominaga ◽  
Shinji Takayanagi ◽  
Takahiko Yanagitani
Keyword(s):  
Acoustic Wave ◽  
Aluminum Nitride ◽  
Piezoelectric Properties ◽  
Negative Ions ◽  
Ion Bombardment ◽  
Low Pressure ◽  
Film Deposition ◽  
Negative Ion ◽  
Sputtering Deposition ◽  
Low Pressures

Abstract Scandium aluminum nitride (ScAlN) films are being actively researched to explore their potential for use in bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators because of their good piezoelectric properties. Sputtering is commonly used in ScAlN film deposition. Unfortunately, it has been reported that film quality metrics such as the crystallinity and piezoelectric properties can deteriorate before the Sc concentration reaches 43% without an isostructural phase transition. One reason for this is bombardment with negative ions generated from carbon and oxygen impurities in the Sc ingots. Because the number of negative ions increases during low-pressure sputtering deposition, their effect on film quality may be considerable. In this study, we investigated negative-ion bombardment of the substrate during sputtering deposition and its effects on ScAlN crystallinity and piezoelectric properties. Negative-ion energy distribution measurements indicated that many more negative ions collide with the substrate during ScAlN film deposition than during AlN deposition. In addition, decreasing the sputtering pressure further increased the number of negative ions and their energies. It is well known that film quality improves at low pressures because increasing the mean free path reduces thermalization and scattering of sputtered particles. Although, AlN crystallinity and piezoelectric properties improved at low pressures, the properties of ScAlN films deteriorated dramatically. Therefore, the results indicated that ion bombardment increase at low pressure adversely effects ScAlN crystal growth, deteriorating crystallinity and piezoelectric properties. ScAlN films may be improved further by suppressing negative-ion bombardment of the substrate.

The Boltzmann relation in electronegative plasmas: When is it permissible to use it?

2000 ◽  
Vol 64 (2) ◽  
pp. 131-153 ◽  
Author(s):  
R. N. FRANKLIN ◽  
J. SNELL
Keyword(s):  
Fluid Model ◽  
Negative Ions ◽  
Ionization Rate ◽  
Negative Ion ◽  
Simple Relationship ◽  
Ion Temperature ◽  
Ion Density ◽  
Positive Ions ◽  
Electronegative Plasmas ◽  
Low Pressures

This paper reports the results of computations to obtain the spatial distributions of the charged particles in a bounded active plasma dominated by negative ions. Using the fluid model with a constant collision frequency for electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation ne = ne0exp(eV/kT) for the electrons of density ne, where the temperature T is approximately the electron temperature Te, and that the density nn of the negative ions at low pressures obeys nn = nn0exp(eV/kTn), where Tn is the negative-ion temperature. However, at high pressure in detachment-dominated gases where the ratio of negative-ion density to electron density is constant and greater than unity, and when the attachment rate is larger than the ionization rate, the negative ions are distributed with the same effective temperature as the electrons. In all other cases there is no simple relationship. Thus to put nn/ne = const, nn = ne0exp(eV/kTe) and nn = nn0exp(eV/kTn) simultaneously is mathematically inconsistent and physically unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients based on these assumptions have no validity. The correct expressions for the situation where nn/ne = const are obtained without invoking a Boltzmann relation for the negative ions.

scholarly journals Mobility of the positive and negative ions in gases at high pressure

1912 ◽  
Vol 86 (584) ◽  
pp. 154-162 ◽  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Mathematical Expression ◽  
Negative Ions ◽  
Negative Ion ◽  
Positive Ions ◽  
Low Pressures ◽  
Positive Ion ◽  
Reduced Pressures

The velocity of ions in gases at reduced pressures was first investigated by Rutherford and by Langevin. Recently the author and others have carried out similar investigations. The results of these investigations show that for the negative ions in air the product of the mobility and the pressure is constant for pressures ranging from 760 mm. to 200 mm. of mercury, but with further reduction the product increases with the reduction of pressure, this increase becoming very great at low pressures. For the positive ions in air the product of the mobility and pressure is constant for pressures investigated between 760 mm. and 3 mm. of mercury. Similar results were obtained for the mobilities of the ions in other gases. The results show that if the ion is an aggregation of molecules, this aggregation becomes, at low pressures, less complex in the ease of the negative ion, while in the ease of the positive ion it persists down to 3 mm. of mercury. The purpose of the present research was the study of the mobilities of both kinds of ions in gases at high pressures. The method of investigation is based on the mathematical expression, developed by Prof. Rutherford, for the current between two plates, assuming that a very intense ionisation exists near the surface of one of the electrodes.

scholarly journals Effect of Negative Ions on the Instability of Ion-acoustic Waves in a Relativistic Plasma

1997 ◽  
Vol 50 (2) ◽  
pp. 319 ◽  
Author(s):  
K. K. Mondal ◽  
S. N. Paul ◽  
A. Roychowdhury
Keyword(s):  
Dispersion Relation ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Negative Ions ◽  
Ion Concentration ◽  
Negative Ion ◽  
Relativistic Velocity ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Ion Acoustic

The dispersion relation of an ion-acoustic wave propagating through a collisionless, unmagnetised plasma, having warm isothermal electrons and cold positive and negative ions has been derived. It is seen that the ion-acoustic wave will be unstable in the presence of streaming of ions. Instability of the wave is graphically analysed for the plasma having (H+, O¯) ions, (H+, O2¯) ions, (H+, SF5¯) ions, (He+, Cl¯) ions and (Ar+, O¯) ions with different negative ion concentration and relativistic velocity.

Piezoelectric Properties of Aluminum Nitride for Thin Film Bulk Acoustic Wave Resonator

2005 ◽  
Vol 47 (92) ◽  
pp. 309 ◽  
Author(s):  
Nam Kuangwoo ◽  
Park Yunkwon ◽  
Ha Byeoungju ◽  
Shim Dongha ◽  
Song Insang ◽  
...  
Keyword(s):  
Thin Film ◽  
Acoustic Wave ◽  
Aluminum Nitride ◽  
Piezoelectric Properties ◽  
Bulk Acoustic Wave ◽  
Bulk Acoustic Wave Resonator ◽  
Wave Resonator ◽  
Film Bulk

scholarly journals Effect of a magnetic force on the motion of negative ions in a gas

1912 ◽  
Vol 87 (596) ◽  
pp. 357-365 ◽  
Keyword(s):  
Charged Particle ◽  
Atmospheric Pressure ◽  
Magnetic Force ◽  
Large Range ◽  
Negative Ions ◽  
Negative Ion ◽  
Electric Force ◽  
Dry Air ◽  
Low Pressures ◽  
Made In

1. When the velocity of a charged particle in a gas is proportional to the electric force and inversely proportional to the pressure, the size of the particle is unaltered either by changes in the pressure or in the force. For a large range of pressures and forces the mass of an ion is thus shown to be constant, since the velocity is proportional to the ratio X / P. At low pressures when the ratio X / P exceeds a certain value the velocity of the negative ions undergoes large changes when small variations are made in the force or in the pressure. The increase in the mobility may be explained on the hypothesis that the mass associated with the negative ion diminishes. Thus in dry air at a pressure of 29 mm. the velocity of the negative ions is 926 cm. per second, under a force of 2·3 volts per centimetre, whereas if the ion travelled with the same mass that it has at atmospheric pressure the velocity would be about 114 cm. per second.

Formation of Negative Ions by Negative-Ion Bombardment of Surfaces: A New Process

Nature ◽  
1939 ◽  
Vol 143 (3620) ◽  
pp. 474-475 ◽  
Author(s):  
R. H. SLOANE ◽  
ELIZA B. CATHCART
Keyword(s):  
Negative Ions ◽  
Ion Bombardment ◽  
Negative Ion ◽  
New Process

Nonlinear dust-acoustic wave propagation in a Lorentzian dusty plasma in presence of negative ions

2018 ◽  
Vol 84 (5) ◽  
Author(s):  
Raicharan Denra ◽  
Samit Paul ◽  
Uttam Ghosh ◽  
Susmita Sarkar
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Negative Ions ◽  
Negative Ion ◽  
Acoustic Wave Propagation ◽  
Dust Acoustic Wave ◽  
Charge Variation ◽  
Dust Charge ◽  
Dust Acoustic ◽  
Adiabatic Dust Charge Variation

In this paper we have studied the effect of the density and temperature of negative ions on the nonlinear dust-acoustic wave propagation in a Lorentzian dusty plasma. We have considered both adiabatic and non-adiabatic dust charge variation. The presence of both low and high populations of negative ions are considered. Separate models have been developed because the two populations give rise to opposite polarity of grain charges. In both models electrons are assumed to follow a kappa velocity distribution while the positive and negative ions satisfy a Maxwellian velocity distribution. Adiabatic dust charge variation shows the propagation of a dust-acoustic soliton in cases of both a high and low population of negative ions whose amplitude depends on the negative ion temperature and negative ion density. On the other hand, non-adiabatic dust charge variation generates a stable oscillatory dust-acoustic shock when the negative ion population is low. An unstable potential has been predicted from this analysis when the negative ion population is high and the dust charge variation is non-adiabatic.

Aluminum Nitride Thin Film Based Surface Acoustic Wave Sensors

2008 ◽  
Author(s):  
A. Kabulski ◽  
V. R. Pagán ◽  
D. Cortes ◽  
R. Burda ◽  
O. M. Mukdadi ◽  
...  
Keyword(s):  
Thin Film ◽  
Acoustic Wave ◽  
Aluminum Nitride ◽  
Surface Acoustic Wave ◽  
Acoustic Wave Sensors ◽  
Wave Sensors
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