creating a vacancy that is filled by electrostatic fields,carrier concen- an outer shell electron.This jump tration,temperature distribution, from an outer to inner shell results spreading resistance,and conduc- e beam in a change in energy that pro- tivity.Many of these techniques duces either a x-ray or Auger consist of looking simultaneously electron.The emitted x-ray has at another signal while performing energy equal to this change.The standard AFM imaging.One of x-rays are then detected by either a the most common techniques for lithium-drifted silicon detector for mapping differences in materials an EDS system,or a gas propor- properties is PhaselmagingTM tional counter detector for a WDS Phaselmaging is conducted during system.A typical x-ray spectrum TappingMode AFM operation by collected with an EDS system is monitoring the phase lag between shown in Figure 10. the oscillating drive signal used to drive the cantilever and the Figure 9.Signals emitted from a sample surface after interaction with an electron beam. Backscattered electrons are the oscillating detection signal from result of beam electrons being the photodiode detector.This scattered back out of the sample. signal will indicate differences in In this case,the incident beam viscoelasticity and/or adhesion electrons undergo a number of across the imaged area.This scattering events within the technique is commonly applied to specimen in which very little mapping the distribution of energy is lost,allowing these polymers in a heterogeneous electrons to go much deeper into system,or mapping the distribu- the sample than secondary tion of filler,such as silica or electrons and still emerge from the carbon black,in a polymer matrix. sample surface to be detected. An example of Phaselmaging on a The percentage of beam electrons polyethylene film is shown in that become backscattered Figure 12.Other ways to get electrons has been found to be similar information are by Force dependent on the atomic number Modulation AFM,which maps Figure 10.EDS X-ray spectrum of an AlGaN thin of the material,which makes it a differences in elasticity across the film on SiC substrate showing the presence of N, useful signal for analyzing the Ga,and Al. sample surface,and Lateral Force material composition.Once these Microscopy(LFM),which maps electrons escape from the surface differences in friction across the they are detected by either the sample surface. Everhart-Thornley detector or a solid state detector.An example There are also techniques that can of a backscattered image of a PbSn be used to investigate long range alloy is shown in Figure 11. forces across the imaged area. Magnetic Force Microscopy AFM/SPM (MFM)and Electric Force Microscopy(EFM)map the Although an AFM does not magnetic and electrostatic field provide elemental analysis,it can gradients,respectively,which supply compositional information extend from the sample surface. by differentiating materials based These techniques are performed Figure 11.Backscattered SEM image of an PbSn on physical properties,such as by using either a magnetic or alloy showing contrast based on the atomic number stiffness,elasticity,compliance, conductive probe to map the of the two components.The brighter areas are Pb- friction,adhesion,magnetic and attractive and repulsive forces rich.5.000x.Scale bar=1um.7 creating a vacancy that is filled by an outer shell electron. This jump from an outer to inner shell results in a change in energy that pro￾duces either a x-ray or Auger electron. The emitted x-ray has energy equal to this change. The x-rays are then detected by either a lithium-drifted silicon detector for an EDS system, or a gas propor￾tional counter detector for a WDS system. A typical x-ray spectrum collected with an EDS system is shown in Figure 10. Backscattered electrons are the result of beam electrons being scattered back out of the sample. In this case, the incident beam electrons undergo a number of scattering events within the specimen in which very little energy is lost, allowing these electrons to go much deeper into the sample than secondary electrons and still emerge from the sample surface to be detected. The percentage of beam electrons that become backscattered electrons has been found to be dependent on the atomic number of the material, which makes it a useful signal for analyzing the material composition. Once these electrons escape from the surface they are detected by either the Everhart-Thornley detector or a solid state detector. An example of a backscattered image of a PbSn alloy is shown in Figure 11. AFM/SPM Although an AFM does not provide elemental analysis, it can supply compositional information by differentiating materials based on physical properties, such as stiffness, elasticity, compliance, friction, adhesion, magnetic and electrostatic fields, carrier concen￾tration, temperature distribution, spreading resistance, and conduc￾tivity. Many of these techniques consist of looking simultaneously at another signal while performing standard AFM imaging. One of the most common techniques for mapping differences in materials properties is PhaseImagingTM. PhaseImaging is conducted during TappingMode AFM operation by monitoring the phase lag between the oscillating drive signal used to drive the cantilever and the oscillating detection signal from the photodiode detector. This signal will indicate differences in viscoelasticity and/or adhesion across the imaged area. This technique is commonly applied to mapping the distribution of polymers in a heterogeneous system, or mapping the distribu￾tion of filler, such as silica or carbon black, in a polymer matrix. An example of PhaseImaging on a polyethylene film is shown in Figure 12. Other ways to get similar information are by Force Modulation AFM, which maps differences in elasticity across the sample surface, and Lateral Force Microscopy (LFM), which maps differences in friction across the sample surface. There are also techniques that can be used to investigate long range forces across the imaged area. Magnetic Force Microscopy (MFM) and Electric Force Microscopy (EFM) map the magnetic and electrostatic field gradients, respectively, which extend from the sample surface. These techniques are performed by using either a magnetic or conductive probe to map the attractive and repulsive forces Figure 9. Signals emitted from a sample surface after interaction with an electron beam. Figure 10. EDS X-ray spectrum of an AlGaN thin film on SiC substrate showing the presence of N, Ga, and Al. Figure 11. Backscattered SEM image of an PbSn alloy showing contrast based on the atomic number of the two components. The brighter areas are Pb￾rich. 5,000x, Scale bar=1µm